Fix parsing of imports with module string name in flow plugin (#12224)

packages/babel-parser/test/fixtures/flow/module-string-names/mixed/input.js

@@ -0,0 +1,2 @@
+import { "foo" as bar, "default" as qux } from "module-a";
+export * as "foo", { default as "quux" } from "module-b";