gha: remove old-backports.yml

Looks like this worklfow is not needed because it has been disabled for over 1 year: https://github.com/redpanda-data/redpanda/actions/workflows/old-backports.yml
redpanda-data · Jun 7, 2024 · 4573b58 · 4573b58
1 parent 0be664d
commit 4573b58
Showing 1 changed file with 0 additions and 25 deletions.
diff --git a/.github/workflows/old-backports.yml b/.github/workflows/old-backports.yml