py3 spec: remove python2 dependencies from server-trust-ad

Use only python3 dependencies when building server-trust-ad for python3.

Fixes: https://pagure.io/freeipa/issue/7208
Signed-off-by: Tomas Krizek <tkrizek@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

freeipa.spec.in

@@ -500,10 +500,12 @@ Requires: samba-winbind
 Requires: libsss_idmap
 
 %if 0%{?with_python3}
+Requires(post): python3
 Requires: python3-samba
 Requires: python3-libsss_nss_idmap
 Requires: python3-sss
 %else
+Requires(post): python2
 Requires: python2-samba
 Requires: python2-libsss_nss_idmap
 Requires: python2-sss
@@ -514,7 +516,6 @@ Requires: python2-sss
 # IPA AD trusts cannot be used at the same time with the locator plugin
 # since Winbindd will be configured in a different mode
 Requires(post): %{_sbindir}/update-alternatives
-Requires(post): python
 Requires(postun): %{_sbindir}/update-alternatives
 Requires(preun): %{_sbindir}/update-alternatives