Markdown link checker still not ignoring gnu links

[teutoburg]

Apparently "https://www.gnu.org/licenses/gpl-3.0" does not match "^https://www.gnu.org/licenses.*$", see https://github.com/AstarVienna/ScopeSim/actions/runs/13944620342/job/39028856861?pr=601

I guess this is related to #24

[hugobuddel]

It did work fine previously I thought.. so no clue why it does not worok anymore..