8211882: Broken links in serialized-form.html

Reviewed-by: darcy, lancea

src/java.base/share/classes/java/util/EnumSet.java

@@ -463,7 +463,7 @@ public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>
 
     /**
      * Returns a
-     * <a href="../../serialized-form.html#java.util.EnumSet.SerializationProxy">
+     * <a href="{@docRoot}/serialized-form.html#java.util.EnumSet.SerializationProxy">
      * SerializationProxy</a>
      * representing the state of this instance.
      *

src/java.base/share/classes/java/util/ImmutableCollections.java

@@ -1091,9 +1091,9 @@ final class CollSer implements Serializable {
      * Creates and returns an immutable collection from this proxy class.
      * The instance returned is created as if by calling one of the
      * static factory methods for
-     * <a href="List.html#immutable">List</a>,
-     * <a href="Map.html#immutable">Map</a>, or
-     * <a href="Set.html#immutable">Set</a>.
+     * <a href="List.html#unmodifiable">List</a>,
+     * <a href="Map.html#unmodifiable">Map</a>, or
+     * <a href="Set.html#unmodifiable">Set</a>.
      * This proxy class is the serial form for all immutable collection instances,
      * regardless of implementation type. This is necessary to ensure that the
      * existence of any particular implementation type is kept out of the