Remove redundant guards

* RubyBignum cannot be a RubyDynamicObject.

Author: eregon

src/main/java/org/truffleruby/language/objects/SingletonClassNode.java

@@ -92,20 +92,15 @@ protected RubyClass singletonClassClassUncached(RubyClass rubyClass) {
     }
 
     @Specialization(
-            guards = {
-                    "object == cachedObject",
-                    "!isRubyBignum(cachedObject)",
-                    "!isRubyClass(cachedObject)" },
+            guards = { "object == cachedObject", "!isRubyClass(cachedObject)" },
             limit = "getIdentityCacheLimit()")
     protected RubyClass singletonClassInstanceCached(RubyDynamicObject object,
             @Cached("object") RubyDynamicObject cachedObject,
             @Cached("getSingletonClassForInstance(object)") RubyClass cachedSingletonClass) {
         return cachedSingletonClass;
     }
 
-    @Specialization(
-            guards = { "!isRubyBignum(object)", "!isRubyClass(object)" },
-            replaces = "singletonClassInstanceCached")
+    @Specialization(guards = "!isRubyClass(object)", replaces = "singletonClassInstanceCached")
     protected RubyClass singletonClassInstanceUncached(RubyDynamicObject object) {
         return getSingletonClassForInstance(object);
     }