Remove shebang from bash completions

bash completions are to be sourced. It makes little sense to
execute them.

Detected by Debian's Lintian tool, which warns about non-executable
files that appear to be #! scripts.

Signed-off-by: Simon McVittie <smcv@collabora.com>

Closes: #1119
Approved by: cgwalters

bash/ostree

@@ -1,5 +1,3 @@
-#!/bin/bash
-#
 # bash completion file for ostree commands
 #
 # This script provides completion of: