go.mod: update gitlab dep to v0.30.1

Releases after github.com/xanzy/go-gitlab@v0.31.0 introduce breaking
changes to the NewClient call.

Addresses #94

vendor/github.com/aktau/github-release/release

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+main() {
+    apt-get update && apt-get install zip
+    git branch --set-upstream-to=origin/master release
+    set -x
+    exec /bin/bash -c "$@"
+}
+
+main "$@"