tools/choose-default-locale.sh: set shebang to /bin/sh

The script does not use any bash features.
On NixOS we have /bin/sh and /usr/bin/env for posix compatibility
but not /bin/bash as it is stored in our nix store.
With this change one can run the `meson configure` without patching
which greatly helps, when working on upstream contributions.

tools/choose-default-locale.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 set -e