Avoid "ad" anywhere in the buildId (#6854)
Avoid "ad" anywhere in the buildId (#6854)

* Added a check for ad_ in the buildId

* ad_ > ad

Co-Authored-By: lfades <faea5242a00c52da62a0f00df168c199b7ab748d@zeit.co>

* Update the `ad` comment

Co-Authored-By: lfades <faea5242a00c52da62a0f00df168c199b7ab748d@zeit.co>

* Avoid all buildId's that contain "ad"

Looking through the uBlock Origin filter list, it uses regex wildcards to avoid various things with "ad" anywhere in the string. It's a safe bet to just avoid "ad" all together (as opposed to just at the start).

* Use regex (case incensitive) to check for "ad" 

The following cases will set this regex to true:

```
/ad/i.test("somead")
/ad/i.test("someADlksdjf")
/ad/i.test("adlksdjf")
/ad/i.test("ADlksdjf")
```

JeromeFitz/next.js,flybayer/next.js,flybayer/next.js,JeromeFitz/next.js,flybayer/next.js,BlancheXu/test,BlancheXu/test,azukaru/next.js,azukaru/next.js,zeit/next.js,BlancheXu/test,JeromeFitz/next.js,zeit/next.js,azukaru/next.js,JeromeFitz/next.js,azukaru/next.js,flybayer/next.js,zeit/next.js