describe alternative for unmodifiable/synchronizedNavigableSetNavigableSet for java8 users

Fixes #3283

RELNOTES=n/a
PiperOrigin-RevId: 543436855

Author: kofemann

android/guava/src/com/google/common/collect/Sets.java

@@ -1737,6 +1737,8 @@ static boolean equalsImpl(Set<?> s, @CheckForNull Object object) {
    * <p>The returned navigable set will be serializable if the specified navigable set is
    * serializable.
    *
+   * <p><b>Java 8 users and later:</b> Prefer {@link Collections#unmodifiableNavigableSet}.
+   *
    * @param set the navigable set for which an unmodifiable view is to be returned
    * @return an unmodifiable view of the specified navigable set
    * @since 12.0
@@ -1881,6 +1883,8 @@ public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclus
    * <p>The returned navigable set will be serializable if the specified navigable set is
    * serializable.
    *
+   * <p><b>Java 8 users and later:</b> Prefer {@link Collections#synchronizedNavigableSet}.
+   *
    * @param navigableSet the navigable set to be "wrapped" in a synchronized navigable set.
    * @return a synchronized view of the specified navigable set.
    * @since 13.0

guava/src/com/google/common/collect/Sets.java

@@ -1796,6 +1796,8 @@ static boolean equalsImpl(Set<?> s, @CheckForNull Object object) {
    * <p>The returned navigable set will be serializable if the specified navigable set is
    * serializable.
    *
+   * <p><b>Java 8 users and later:</b> Prefer {@link Collections#unmodifiableNavigableSet}.
+   *
    * @param set the navigable set for which an unmodifiable view is to be returned
    * @return an unmodifiable view of the specified navigable set
    * @since 12.0
@@ -1962,6 +1964,8 @@ public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclus
    * <p>The returned navigable set will be serializable if the specified navigable set is
    * serializable.
    *
+   * <p><b>Java 8 users and later:</b> Prefer {@link Collections#synchronizedNavigableSet}.
+   *
    * @param navigableSet the navigable set to be "wrapped" in a synchronized navigable set.
    * @return a synchronized view of the specified navigable set.
    * @since 13.0