Update xml/System.Collections.Frozen/FrozenDictionary`2.xml

Co-authored-by: Carlos Sánchez López <[email protected]>

Author: eiriktsarpalis

xml/System.Collections.Frozen/FrozenDictionary`2.xml

@@ -1227,7 +1227,8 @@
           Gets an instance of a type that may be used to perform operations on a <see cref="T:System.Collections.Frozen.FrozenDictionary`2"/>
           using a <typeparamref name="TAlternateKey"/> as a key instead of a <typeparamref name="TKey"/>.
         </summary>
-        <returns>true if a lookup could be created; otherwise, false.</returns>
+        <returns>
+          <see langword="true" /> if a lookup could be created; otherwise, <see langword="false" />.</returns>
         <remarks>
           This instance must be using a comparer that implements <see cref="T:System.Collections.Generic.IAlternateEqualityComparer`2"/> with
           <typeparamref name="TAlternateKey"/> and <typeparamref name="TKey"/>. If it doesn't, the method will return false.