gerrit: Don't include '.' in the match for adjecent separator

The regex has a deeper flaw that causes it to actually include
the separator (e.g. "commit:ad53840" results in ":ad53840" being
the link label), but that's for another time to fix.

This ensures urls like the following don't break:

https://github.com/leafo/lessphp/compare/785ad53840...6e8e724fc7

I think the benefit from this is worth more then the arguable
flipside that people who don't separate sentences with a space
after the full stop and use a hash as the first word of the next
sentence don't get their hash linked.0be25f0bfe, like that.
A hash after a normal sentence split. 0be25f0bfe like that, will
still be linked.

Change-Id: I80ca4a17a229c0fb1b41fd29ffec5f17dce9dc5f
Merge "gerrit: Don't include '.' in the match for adjecent separator" into production