Rely entirely on sourceType for module vs script differentiation. (#7417)

packages/babel-plugin-transform-modules-commonjs/src/index.js

@@ -98,9 +98,7 @@ export default function(api, options) {
     visitor: {
       Program: {
         exit(path) {
-          // For now this requires unambiguous rather that just sourceType
-          // because Babel currently parses all files as sourceType:module.
-          if (!isModule(path, true /* requireUnambiguous */)) return;
+          if (!isModule(path)) return;
 
           // Rename the bindings auto-injected into the scope so there is no
           // risk of conflict between the bindings.