Revert "chore: prefer .tsx? files over .jsx? file extensions (#3909)"

This reverts commit c3b6519.

Author: haoqunjiang

packages/@vue/cli-plugin-typescript/index.js

@@ -15,8 +15,7 @@ module.exports = (api, options) => {
 
     config.resolve
       .extensions
-        .prepend('.ts')
-        .prepend('.tsx')
+        .merge(['.ts', '.tsx'])
 
     const tsRule = config.module.rule('ts').test(/\.ts$/)
     const tsxRule = config.module.rule('tsx').test(/\.tsx$/)