Frontend: Remove the temporary Actors2 feature definition.

Author: tshortli

include/swift/Basic/Features.def

@@ -64,7 +64,6 @@ LANGUAGE_FEATURE(AsyncAwait, 296, "async/await", true)
 LANGUAGE_FEATURE(EffectfulProp, 310, "Effectful properties", true)
 LANGUAGE_FEATURE(MarkerProtocol, 0, "@_marker protocol", true)
 LANGUAGE_FEATURE(Actors, 0, "actors", true)
-LANGUAGE_FEATURE(Actors2, 0, "actors #2 (TEMPORARY)", true)
 LANGUAGE_FEATURE(ConcurrentFunctions, 0, "@concurrent functions", true)
 LANGUAGE_FEATURE(RethrowsProtocol, 0, "@rethrows protocol", true)
 LANGUAGE_FEATURE(GlobalActors, 316, "Global actors", true)

lib/AST/ASTPrinter.cpp

@@ -2738,10 +2738,6 @@ static bool usesFeatureConcurrentFunctions(Decl *decl) {
   return false;
 }
 
-static bool usesFeatureActors2(Decl *decl) {
-  return false;
-}
-
 static bool usesFeatureSendable(Decl *decl) {
   if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
     if (func->isSendable())