Fix FSEventStreamScheduleWithRunLoop deprecation warning on macOS 13+

[ndbroadbent]

Replace the deprecated FSEventStreamScheduleWithRunLoop API with the modern FSEventStreamSetDispatchQueue API that uses Grand Central Dispatch.

This eliminates the deprecation warning while maintaining the same functionality for file system event monitoring on macOS, e.g. when running tests in convox/convox:

❯ make test
env TEST=true go test -covermode atomic -coverprofile coverage.txt -mod=vendor ./...
?   	github.com/convox/convox	[no test files]
# github.com/convox/changes
cgo-gcc-prolog:116:2: warning: 'FSEventStreamScheduleWithRunLoop' is deprecated: first deprecated in macOS 13.0 - Use FSEventStreamSetDispatchQueue instead. [-Wdeprecated-declarations]
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/FSEvents.framework/Headers/FSEvents.h:1159:1: note: 'FSEventStreamScheduleWithRunLoop' has been explicitly marked deprecated here

[ndbroadbent]

@nightfury1204 I was wondering if you could please take a look at this? thanks!

[nightfury1204]

Thanks for the pr.It would be better if we can deprecate this library and replace it with actively managed library.

[ndbroadbent]

Hey sure I totally agree! I was just wanting to get rid of the deprecation warnings but either way is good.