Remove WatchPaths from launch daemon

[aysiu]

From man launchd.plist:

     WatchPaths <array of strings>
     This optional key causes the job to be started if any one of the listed
     paths are modified.

     IMPORTANT: Use of this key is highly discouraged, as filesystem event
     monitoring is highly race-prone, and it is entirely possible for
     modifications to be missed. When modifications are caught, there is no
     guarantee that the file will be in a consistent state when the job is
     launched.

This section being removed doesn't seem to impede Crypt's operation (in fact, it may help address https://github.com/grahamgilbert/crypt/issues/128—can't be 100% sure on that, though).