Fix `brew audit` regex requring the word `raw` to end the string, by removing anchor.

Caught grepping around for patch URLs. That is, the anchor at the end of the
regex here causes these non-revisioned URLs to slip through:
```
libgsm: https://gist.github.com/dholm/5840964/raw/
libqxt: https://gist.github.com/uranusjr/6019051/raw/
reaver: https://gist.github.com/syndicut/6134996/raw/reaver-osx.diff
```
Take out that `$`, and these are now correctly found.

No false positives that I can detect.  Sans patch, clean checkout:
`Error: 3 problems in 2 formulae`, with patch: `Error: 6 problems in 5 formulae`.