emacs: Remove notmuch-mua-message-send-hook

emacs: Remove notmuch-mua-message-send-hook

Currently `message-send-hook` functions are being called twice: In
notmuch send common when `notmuch-mua-send-hook` functions are
run (which by default includes `notmuch-mua-message-send-hook`) and in
`message-send` itself.

Because `message-send-hook` functions are run in `message-send` itself,
we don't need also need to run them before we delegate to `message-send`

Calling `notmuch-mua-message-send-hook` resulted in functions in
`message-send-hook` to be called twice. This causes bugs in
non-idempotent hook functions.