Move to using "well-known" SkyFunctionNames in tests exercising graph

--
MOS_MIGRATED_REVID=105539869
diff --git a/src/test/java/com/google/devtools/build/skyframe/GraphTester.java b/src/test/java/com/google/devtools/build/skyframe/GraphTester.java
index 04d76db..f7c2da4 100644
--- a/src/test/java/com/google/devtools/build/skyframe/GraphTester.java
+++ b/src/test/java/com/google/devtools/build/skyframe/GraphTester.java
@@ -45,7 +45,7 @@
  */
 public class GraphTester {
 
-  public static final SkyFunctionName NODE_TYPE = SkyFunctionName.create("Type");
+  public static final SkyFunctionName NODE_TYPE = SkyFunctionName.FOR_TESTING;
 
   private final Map<SkyKey, TestFunction> values = new HashMap<>();
   private final Set<SkyKey> modifiedValues = new LinkedHashSet<>();