[Stdlib] Add forgotten @IgnorableReturnValue on MutableEntry.setValue

It was added to Jvm, but missing in common and JS.
Setting it helps with consistency between expects and actuals (see KT-77593)

Author: sandwwraith

libraries/stdlib/js/builtins/Collections.kt

@@ -780,6 +780,7 @@ public actual interface MutableMap<K, V> : Map<K, V> {
          *
          * @return the previous value corresponding to the key.
          */
+        @IgnorableReturnValue
         public actual fun setValue(newValue: V): V
     }
 

libraries/stdlib/src/kotlin/Collections.kt

@@ -716,6 +716,7 @@ public expect interface MutableMap<K, V> : Map<K, V> {
          *
          * @return the previous value corresponding to the key.
          */
+        @IgnorableReturnValue
         public fun setValue(newValue: V): V
     }
 }