fetch: do set prune when testing

We load the remote again, so we need to ask the new remote to prune the
refs, or we're not exercising the code in our tests.

tests/network/fetchlocal.c

@@ -159,6 +159,7 @@ void test_network_fetchlocal__prune_overlapping(void)
 	cl_git_pass(git_config_set_multivar(config, "remote.origin.fetch", "^$", "refs/heads/*:refs/remotes/origin/*"));
 
 	cl_git_pass(git_remote_lookup(&origin, repo, GIT_REMOTE_ORIGIN));
+	git_remote_set_prune_refs(origin, true);
 	git_remote_set_callbacks(origin, &callbacks);
 	cl_git_pass(git_remote_fetch(origin, NULL, NULL, NULL));