win-capture: Update hooked state before unhooked signal

[EZ64cool]

Description

Updates the stop_capture call to set capturing to false before sending the unhooked signal.

Motivation and Context

If the get_hooked procedure is called during the unhooked signal the source would still report that it's hooked because gc->capturing hasn't been updated yet. This is mainly an issue when enumerating all capture sources to see if any are still capturing after an unhooked signal.

How Has This Been Tested?

Tested on windows 10 x64 and it now works as expected. It's a very isolated change so easy to test.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.