[5.x] Don't overlap git commits

[edalzell]

Closes #11322

[edalzell]

@jesseleite I rolled this out to production and got this error:

Request URL: https://www.zakat.org/
Request data: []
Statamic\Git\CommitJob has been attempted too many times.
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/MaxAttemptsExceededException.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/MaxAttemptsExceededException.php) (24)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php) (794)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php) (528)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php) (431)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php) (392)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Worker.php) (178)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Console/WorkCommand.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Console/WorkCommand.php) (149)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Console/WorkCommand.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Queue/Console/WorkCommand.php) (132)
/home/forge/[www.zakat.org/vendor/laravel/horizon/src/Console/WorkCommand.php](http://www.zakat.org/vendor/laravel/horizon/src/Console/WorkCommand.php) (51)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Container/BoundMethod.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Container/BoundMethod.php) (36)
/home/forge/[www.zakat.org/vendor/laravel/framework/src/Illuminate/Container/Util.php](http://www.zakat.org/vendor/laravel/framework/src/Illuminate/Container/Util.php) (43)

So I guess it tried 3 times, failed, then threw an exception?

Suggestions on best way to handle? Like if the lock goes away on its own later those commits will be handled, but there's no guarantee that there's another content change, so I'd rather ensure these actually get committed.

Let's discuss.

[edalzell]

Not worth it right now, will leave the issue open and switch to scheduled commits.