Remove unneeded branch from getHelperName (#36998)

Author: weswigham

src/compiler/checker.ts

@@ -35668,7 +35668,6 @@ namespace ts {
                 case ExternalEmitHelpers.ClassPrivateFieldGet: return "__classPrivateFieldGet";
                 case ExternalEmitHelpers.ClassPrivateFieldSet: return "__classPrivateFieldSet";
                 case ExternalEmitHelpers.CreateBinding: return "__createBinding";
-                case ExternalEmitHelpers.SetModuleDefault: return "__setModuleDefault";
                 default: return Debug.fail("Unrecognized helper");
             }
         }

src/compiler/types.ts

@@ -5837,10 +5837,9 @@ namespace ts {
         MakeTemplateObject = 1 << 17,   // __makeTemplateObject (used for constructing template string array objects)
         ClassPrivateFieldGet = 1 << 18, // __classPrivateFieldGet (used by the class private field transformation)
         ClassPrivateFieldSet = 1 << 19, // __classPrivateFieldSet (used by the class private field transformation)
-        CreateBinding = 1 << 20,        // __createBinding (use by the module transform for exports and namespace imports)
-        SetModuleDefault = 1 << 21,     // __setModuleDefault (use by the module transform for default exports)
+        CreateBinding = 1 << 20,        // __createBinding (use by the module transform for (re)exports and namespace imports)
         FirstEmitHelper = Extends,
-        LastEmitHelper = SetModuleDefault,
+        LastEmitHelper = CreateBinding,
 
         // Helpers included by ES2015 for..of
         ForOfIncludes = Values,