Fix: stop ignoring --config-file cypress option

Since we always call `removeArg(rawArgs, 'config')`, and since the `matchRE` matches `--config` as well as `--config-file`, we end up ignoring the `--config-file` option if it is provided without the "=" (`--config-file my-config.json`).
This commit fixes this by ensuring that calling `removeArg('config')` removes `--config` without removing `--config-file`.

packages/@vue/cli-plugin-e2e-cypress/index.js

@@ -53,7 +53,7 @@ module.exports.defaultModes = {
 }
 
 function removeArg (rawArgs, argToRemove, offset = 1) {
-  const matchRE = new RegExp(`^--${argToRemove}`)
+  const matchRE = new RegExp(`^--${argToRemove}$`)
   const equalRE = new RegExp(`^--${argToRemove}=`)
   const i = rawArgs.findIndex(arg => matchRE.test(arg))
   if (i > -1) {