Reduce CloseLiveBrowser() timeout

I reduced timeout from 180 seconds to 10 seconds.

When researching https://github.com/adobe/brackets/issues/3243, I noticed that my cpu would hit 100% for the full 3 minutes waiting for this to timeout! Lately, I have noticed my cpu fan turning on and discovered instances of Brackets.exe running at 100% cpu, so this may be the cause.