fix bug 1082596 - fix removeUtms regex and replace

To spot-check, go to https://developer-local.allizom.org/en-US/?utm_campaign=test&utm_source=test.com&utm_medium=url and the location should update to https://developer-local.allizom.org/en-US/ after the `pageview` is sent to GA.

The code was looking for `#utm_` params, which we use for hacks.mozilla.org. We use regular `?utm_` params for MDN. In addition, the `ga('send'` call was trying to remove the parameters **before** the `pageview`, so it's a good thing it **wasn't** working.