Revert "[ConstraintSystem] Use semantics providing exprs when dealing with favored types."

This reverts commit 2f80af15ec.

I expected this to have no effect, but it results in one of the
expression type checker tests taking longer, so that test was disabled.

This commit also re-enables the test since it now passes again.

lib/Sema/CSGen.cpp

@@ -916,6 +916,18 @@ namespace {
         }
       }
       
+      // If the paren expr has a favored type, and the subExpr doesn't,
+      // propagate downwards. Otherwise, propagate upwards.
+      if (auto parenExpr = dyn_cast<ParenExpr>(expr)) {
+        if (!CS.getFavoredType(parenExpr->getSubExpr())) {
+          CS.setFavoredType(parenExpr->getSubExpr(),
+                            CS.getFavoredType(parenExpr));
+        } else if (!CS.getFavoredType(parenExpr)) {
+          CS.setFavoredType(parenExpr,
+                            CS.getFavoredType(parenExpr->getSubExpr()));
+        }
+      }
+      
       return { true, expr };
     }
     
@@ -1607,6 +1619,10 @@ namespace {
     }
 
     virtual Type visitParenExpr(ParenExpr *expr) {
+      if (auto favoredTy = CS.getFavoredType(expr->getSubExpr())) {
+        CS.setFavoredType(expr, favoredTy);
+      }
+
       auto &ctx = CS.getASTContext();
       auto parenType = CS.getType(expr->getSubExpr())->getInOutObjectType();
       auto parenFlags = ParameterTypeFlags().withInOut(expr->isSemanticallyInOutExpr());