Make $wgLocalStylePath the same as $wgStylePath
The other /static urls SHOULD be relative, whereas this one MUST be relative.
Added a comment to document this fact.
We honour this SHOULD (since we don't use bits.wikimedia.org anymore),
however these variables still varied for no particular reason (/static vs /w/static).
Remove this unimportant difference to make maintenance easier (and improve caching).