Update mapbox-gl-geocoder.css

[joewoodhouse]

Remove weird escape character which was causing my build (when importing this file into another SASS file) to fail.

• briefly describe the changes in this PR
• write tests for all new functionality
• run npm run docs and commit changes to API.md
• update CHANGELOG.md with changes under master heading before merging

[andrewharvey]

@katydecorah looks like this was something you introduced, I assume just an accident and we can safely remove it?

[katydecorah]

This was introduced in 450a567 - I believe it's a CSS hack to target certain versions of IE (ref: https://code.tutsplus.com/tutorials/quick-tip-how-to-target-ie6-ie7-and-ie8-uniquely-with-4-characters--net-10575). I think it's safe to remove, but would recommend that this branch is tested in IE to double check.

[andrewharvey]

Confirmed still works and has the dotted outline on focus on IE11 so looks fine to me.

[andrewharvey]

The build failure is unrelated so I'll merge.