Remove "copy labels from linked issues" github workflow (#36854)

[It still doesn't
work.](https://github.com/ppy/osu/actions/runs/22759488243/job/66012293202)

Looking at the [job
output](https://github.com/ppy/osu/actions/runs/22759488243/job/66012293202#step:1:21)
it appears that the permissions of the `GITHUB_TOKEN` are
*automatically* constrained to `read` even if you request more scopes.
Would be nice if that was *actually documented* somewhere!

Also given supply-chain attacks that people are running on github [via
*issue titles* these
days](https://grith.ai/blog/clinejection-when-your-ai-tool-installs-another)
I'm not sure we want any automation near where it can reach code. Sure,
much of the fault in the aforementioned attack was the fault of meatbags
trusting clankers *WAY* too much, which is a mistake we *would not* do,
but given everpresent software degradation *from unknown sources and for
unknown reasons* let's not ~~COPILOT~~ *ahem* tempt fate...

.github/workflows/pull-request-copy-labels.yml

@@ -1,20 +0,0 @@
-name: Copy labels from linked issues
-
-on:
-  pull_request:
-    types: [opened]
-
-permissions:
-  issues: write
-  pull-requests: write
-  contents: read
-
-jobs:
-  copy-labels:
-    runs-on: ubuntu-latest
-    name: Copy labels from linked issues
-    steps:
-      - name: Copy labels
-        uses: michalvankodev/copy-issue-labels@v1.3.0
-        with:
-          repo-token: ${{ secrets.GITHUB_TOKEN }}