Fix stack overflow in RemoteVstPlugin

[DomClark]

Fixes #4142.

VST plugins use the audioMasterAutomate callback to notify the host of parameter changes from within the plugin, and the host uses the setParameter function to update the plugin with parameter changes from the host. Neither of these should be called in response to the other as the other party already has the necessary information. The issue arises because both Transient and LMMS both do this, so it could be considered a bug in the plugin as much as one in LMMS, but we can and probably ought to fix the issue on our end at least.

This PR removes the setParameter call from the audioMasterAutomate handler.

[zonkmachine]

Merge?

[PhysSong]

This is an one-liner and should bring no side effects as the description says. So I'd say go.
@DomClark FYI, you can merge your pull request yourself when you feel comfortable. Squash and Merge looks like the best merge method for this PR.