bash-completion: add bits to dist tarball

bash-completion: add bits to dist tarball

The bits command was added in commit 6e1301d59 (text-utils: add bits
command) but the bash-completion file was not added to the autotools
Makemodule.am, causing it to be missing from release tarballs.

This resulted in meson build failures when using the tarball with
bash-completion installed, as meson.build references the file but
it doesn't exist in the tarball.

Fixes: https://github.com/util-linux/util-linux/issues/3766
Signed-off-by: Karel Zak <kzak@redhat.com>