contrib: rm init from bash completion

Commit 7a0302f0d7 already removed "runc init" from runc help output,
as this is an internal option not supposed to be used by the end user.

Let's remove runc init completion, too.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

contrib/completions/bash/runc

@@ -771,7 +771,6 @@ _runc() {
 		delete
 		events
 		exec
-		init
 		kill
 		list
 		pause