update runner for fossa workflow (#480)

The workflow was running in opentelemetry-collector-contrib on ubuntu-slim without any issues.

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>

Author: codeboten

.github/workflows/fossa.yml

@@ -16,7 +16,7 @@ jobs:
   fossa:
     name: FOSSA scanning
     if: github.repository_owner == 'open-telemetry'
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     permissions:
       contents: read # for actions/checkout
     steps: