Reduce the enter key delay in the search dialog

[robxnano]

This was originally reported in https://github.com/mate-desktop/pluma/issues/196, but there wasn't really a satisfactory outcome. The scrolling animation that was brought up there is only part of the reason for the delay. There's also an animation on the Find button itself which slows down the search process. This makes holding down the enter key to scroll through a large number of results much slower compared to holding down Ctrl+G. This patch bypasses the Find button activation and sends the response signal instantly, which speeds up the process significantly.

[lukefromdc]

Also note that making keyboard-only navigation more difficult by hiding a button's reaction will create real accessability issues. Try using the interface with ONLY the keyboard, as though your mouse just died and you had work to finish or a relative dependent on Orca was using it.