ci: allow concurrent "Makefile" workflows

I like to push my commits one by one so they all get
the full CI validation.
This limits forces me to push a commit, and wait for the result before
pushing another.

.github/workflows/makefile.yml

@@ -9,10 +9,6 @@ permissions:
   actions: read
   contents: read
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
-
 env:
   GINKGO_PROCS: --procs=1