fix: move the GRPC cache generation workflow into it's own concurrency group (#2071)

Signed-off-by: Chris Jowett <421501+cryptk@users.noreply.github.com>

.github/workflows/generate_grpc_cache.yaml

@@ -4,7 +4,7 @@ on:
 - workflow_dispatch
 
 concurrency:
-  group: ci-${{ github.head_ref || github.ref }}-${{ github.repository }}
+  group: grpc-cache-${{ github.head_ref || github.ref }}-${{ github.repository }}
   cancel-in-progress: true
 
 jobs: