Javadoc: fix examples using markdown instead of @code (#6346)

Author: akarnokd

src/main/java/io/reactivex/Flowable.java

@@ -8846,7 +8846,7 @@ public final <K> Flowable<T> distinct(Function<? super T, K> keySelector,
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Backpressure:</b></dt>
      *  <dd>The operator doesn't interfere with backpressure which is determined by the source {@code Publisher}'s
@@ -8889,7 +8889,7 @@ public final Flowable<T> distinctUntilChanged() {
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Backpressure:</b></dt>
      *  <dd>The operator doesn't interfere with backpressure which is determined by the source {@code Publisher}'s
@@ -8928,7 +8928,7 @@ public final <K> Flowable<T> distinctUntilChanged(Function<? super T, K> keySele
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Backpressure:</b></dt>
      *  <dd>The operator doesn't interfere with backpressure which is determined by the source {@code Publisher}'s

src/main/java/io/reactivex/Observable.java

@@ -7879,7 +7879,7 @@ public final <K> Observable<T> distinct(Function<? super T, K> keySelector, Call
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Scheduler:</b></dt>
      *  <dd>{@code distinctUntilChanged} does not operate by default on a particular {@link Scheduler}.</dd>
@@ -7918,7 +7918,7 @@ public final Observable<T> distinctUntilChanged() {
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Scheduler:</b></dt>
      *  <dd>{@code distinctUntilChanged} does not operate by default on a particular {@link Scheduler}.</dd>
@@ -7953,7 +7953,7 @@ public final <K> Observable<T> distinctUntilChanged(Function<? super T, K> keySe
      * {@code CharSequence}s or {@code List}s where the objects will actually have the same
      * references when they are modified and {@code distinctUntilChanged} will evaluate subsequent items as same.
      * To avoid such situation, it is recommended that mutable data is converted to an immutable one,
-     * for example using `map(CharSequence::toString)` or `map(list -> Collections.unmodifiableList(new ArrayList<>(list)))`.
+     * for example using {@code map(CharSequence::toString)} or {@code map(list -> Collections.unmodifiableList(new ArrayList<>(list)))}.
      * <dl>
      *  <dt><b>Scheduler:</b></dt>
      *  <dd>{@code distinctUntilChanged} does not operate by default on a particular {@link Scheduler}.</dd>