[Typechecker] Remove 'NSObject.hashValue' warning now that it is an error (and because 'hashValue' is longer 'open') (#29328)

Author: theblixguy

include/swift/AST/DiagnosticsSema.def

@@ -4730,9 +4730,6 @@ WARNING(non_exhaustive_switch_unknown_only,none,
         "switch covers known cases, but %0 may have additional unknown values"
         "%select{|, possibly added in future versions}1", (Type, bool))
 
-WARNING(override_nsobject_hashvalue_warning,none,
-        "override of 'NSObject.hashValue' is deprecated; "
-        "did you mean to override 'NSObject.hash'?", ())
 ERROR(override_nsobject_hashvalue_error,none,
       "'NSObject.hashValue' is not overridable; "
       "did you mean to override 'NSObject.hash'?", ())

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1859,16 +1859,6 @@ static bool checkSingleOverride(ValueDecl *override, ValueDecl *base) {
     diagnoseOverrideForAvailability(override, base);
   }
 
-  // Overrides of NSObject.hashValue are deprecated; one should override
-  // NSObject.hash instead.
-  // FIXME: Remove this when NSObject.hashValue becomes non-open in
-  // swift-corelibs-foundation.
-  if (isNSObjectHashValue(base) &&
-      base->hasOpenAccess(override->getDeclContext())) {
-    override->diagnose(diag::override_nsobject_hashvalue_warning)
-      .fixItReplace(SourceRange(override->getNameLoc()), "hash");
-  }
-
   /// Check attributes associated with the base; some may need to merged with
   /// or checked against attributes in the overriding declaration.
   AttributeOverrideChecker attrChecker(base, override);