Only trigger doc gen if it is not a pytorchbot commit (#2909)

Author: lanluo-nvidia

.github/workflows/docgen.yml

@@ -11,6 +11,7 @@ on:
 jobs:
   build-docs:
     runs-on: linux.g5.4xlarge.nvidia.gpu
+    if: ${{ ! contains(github.actor, 'pytorchbot') }}
     environment: pytorchbot-env
     container:
       image: docker.io/pytorch/manylinux-builder:cuda12.1