Update to new runner size syntax

See https://nfcore.slack.com/archives/C050DNB6K5H/p1762184179238379 for details

Author: mashehu

.github/workflows/nf-test.yml

@@ -64,7 +64,7 @@ jobs:
     runs-on: # use self-hosted runners
       - runs-on=${{ github.run_id }}-nf-test
       - runner=4cpu-linux-x64
-      - disk=large
+      - volume=80gb
     strategy:
       fail-fast: false
       matrix: