[gnome-bootstrap-theme] ci: use sh instead of bash

[Guillaume Bernard <gbernard src gnome org>]

commit c72bcc9c5ee3f9871d295c84acde06e8498421ce
Author: Guillaume Bernard <associations guillaume-bernard fr>
Date:   Mon Sep 26 13:15:53 2022 +0200

    ci: use sh instead of bash

 build_deneb_theme.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build_deneb_theme.sh b/build_deneb_theme.sh
index ae7c2a7..0bca006 100755
--- a/build_deneb_theme.sh
+++ b/build_deneb_theme.sh
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/usr/bin/env sh
 
 BOOTSTRAP_VERSION="$(grep bootstrap package.json | sed 
"s/\"bootstrap\":\s\"\^\([[:digit:]]\.[[:digit:]]\).*\"/\1/" | tr -d " ")"