Drop superfluous handling of bash and zsh completion files

/usr/share/bash-completion/completions is owned by the ubiquitous
filesystem package (and bash-completion). This package shouldn't own it.

/usr/share/bash-completion/completions/hg is already installed by
setup.py . zsh is also installed by setup.py, but as _hg . List both
files with the right macros and explicitly, even though it temporarily
will list the files twice since they also are in the file list.

This change was isolated and documented (and obfuscated?) by Mads Kiilerich.

mercurial.spec

@@ -22,7 +22,6 @@ URL: https://mercurial-scm.org/
 Source0: https://www.mercurial-scm.org/release/%{name}-%{upstreamversion}.tar.gz
 Source1: mercurial-site-start.el
 BuildRequires: make
-BuildRequires: bash-completion
 BuildRequires: emacs-el
 BuildRequires: emacs-nox
 BuildRequires: gcc
@@ -177,14 +176,6 @@ grep 'hgk.py*' < %{name}.files > %{name}-hgk.files
 install -D -m 755 contrib/hgk       %{buildroot}%{_libexecdir}/mercurial/hgk
 install -m 755 contrib/hg-ssh       %{buildroot}%{_bindir}
 
-bash_completion_dir=%{buildroot}$(pkg-config --variable=completionsdir bash-completion)
-mkdir -p $bash_completion_dir
-install -m 644 contrib/bash_completion $bash_completion_dir/hg
-
-zsh_completion_dir=%{buildroot}%{_datadir}/zsh/site-functions
-mkdir -p $zsh_completion_dir
-install -m 644 contrib/zsh_completion $zsh_completion_dir/_mercurial
-
 mkdir -p %{buildroot}%{_emacs_sitelispdir}/mercurial
 
 pushd contrib
@@ -235,12 +226,10 @@ rm -rf %{buildroot}%{python3_sitearch}/mercurial/locale
 %doc %attr(644,root,root) %{_mandir}/man?/hg*
 %doc %attr(644,root,root) contrib/*.svg
 %dir %{python3_sitearch}/%{name}-*-py*.egg-info
-%dir %{_datadir}/zsh/
-%dir %{_datadir}/zsh/site-functions/
 %dir %{_sysconfdir}/mercurial
 %dir %{_sysconfdir}/mercurial/hgrc.d
-%dir %{_datadir}/bash-completion/
-%{_datadir}/zsh/site-functions/_mercurial
+%{bash_completions_dir}/hg
+%{zsh_completions_dir}/_hg
 %exclude %{python3_sitearch}/mercurial/rustext%{python3_ext_suffix}
 %{python3_sitearch}/mercurial/
 %{python3_sitearch}/hgext/