[Concurrency] Always downgrade concurrent_access_of_local_capture to a

warning until Swift 6.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -3586,7 +3586,7 @@ namespace {
             loc, diag::concurrent_access_of_local_capture,
             parent.dyn_cast<LoadExpr *>(),
             var)
-          .warnUntilSwiftVersionIf(preconcurrencyContext, 6);
+          .warnUntilSwiftVersion(6);
         return true;
       }