tmux: Drop copycat

Native regex searches are supported since 3.1. And we have never used
the predefined searches feature supported by copycat.

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "tmux/.tmux/plugins/tmux-copycat"]
-	path = tmux/.tmux/plugins/tmux-copycat
-	url = https://github.com/tmux-plugins/tmux-copycat.git
 [submodule "tmux/.tmux/plugins/tmux-open"]
 	path = tmux/.tmux/plugins/tmux-open
 	url = https://github.com/tmux-plugins/tmux-open.git

tmux/.tmux.conf

@@ -159,7 +159,6 @@ set-window-option -g window-status-format "#[bg=colour239,fg=colour237,noitalics
 
 # Plugins
 run-shell '~/.tmux/plugins/tmux-yank/yank.tmux'
-run-shell '~/.tmux/plugins/tmux-copycat/copycat.tmux'
 run-shell '~/.tmux/plugins/tmux-open/open.tmux'
 run-shell '~/.tmux/plugins/tmux-butler/tmux-butler.tmux'
 run-shell '~/.tmux/plugins/tmux-fuzzback/fuzzback.tmux'

tmux/.tmux/plugins/tmux-copycat

@@ -1 +0,0 @@
-Subproject commit d7f7e6c1de0bc0d6915f4beea5be6a8a42045c09