Remove a redundant if condition in Resync()

b/c find_installations() filters by `tenant_pk' if it returns
1 record it means it has already been configured. This
if condition is not needed b/c it checks whether or not the AppInst
is configured which were sure it is.

tcms_github_app/views.py

@@ -112,16 +112,8 @@ def get(self, request, *args, **kwargs):
             )
             return HttpResponseRedirect('/')
 
+        # user .first() b/c the result is a query set
         installation = installations.first()
-        if not installation.tenant_pk:
-            messages.add_message(
-                request,
-                messages.WARNING,
-                _('Unconfigured GitHub App %d') % installation.installation,
-            )
-            return HttpResponseRedirect('/')
-
-        # finally start syncing
         utils.resync(request, installation)
         return HttpResponseRedirect('/')