Remove ancient disclaimer from primary invalidation implementation

The referred-to "alternative" MemoizingEvaluator implementation has been
primary for something like seven years.

PiperOrigin-RevId: 420323298
diff --git a/src/main/java/com/google/devtools/build/skyframe/InvalidatingNodeVisitor.java b/src/main/java/com/google/devtools/build/skyframe/InvalidatingNodeVisitor.java
index d37287c..153da4a 100644
--- a/src/main/java/com/google/devtools/build/skyframe/InvalidatingNodeVisitor.java
+++ b/src/main/java/com/google/devtools/build/skyframe/InvalidatingNodeVisitor.java
@@ -63,8 +63,6 @@
  * internally it spawns many worker threads to process the graph. The thread-safety of the workers
  * on the graph can be delicate, and is documented below. Moreover, no other modifications to the
  * graph can take place while invalidation occurs.
- *
- * <p>This is intended only for use in alternative {@code MemoizingEvaluator} implementations.
  */
 public abstract class InvalidatingNodeVisitor<GraphT extends QueryableGraph> {
   private static final GoogleLogger logger = GoogleLogger.forEnclosingClass();