CI: Switch to L4 runners to see if that helps with timeouts and flakiness.

Author: brycelelbach

.github/workflows/test-brev-tutorial-docker-images.yml

@@ -19,7 +19,7 @@ on:
 jobs:
   test-tutorial:
     name: test-tutorial (${{ inputs.tutorial }})
-    runs-on: linux-amd64-gpu-t4-latest-1
+    runs-on: linux-amd64-gpu-l4-latest-1
     defaults:
       run:
         working-directory: ${{ github.workspace }}