Don't use shebang for bash completion file
Bash completions are meant to be sourced, not executed, so remove the shebang line.
Debian lintian complains about it:
W: xfconf: bash-completion-with-hashbang usr/share/bash-completion/completions/xfconf-query
N:
W: bash-completion-with-hashbang
N:
N: This file starts with the #! sequence that marks interpreted scripts,
N: but it is a bash completion script that is merely intended to be
N: sourced.
N:
N: Please remove the line with hashbang, including any designated
N: interpreter.
N:
N: Refer to
N: https://salsa.debian.org/lintian/lintian/-/merge_requests/292#note_139494
N: for details.
N:
N: Severity: warning
N:
N: Check: scripts
N: