ci: remove unnecessary tmate action (apache#6367)

.github/workflows/chaos.yml

@@ -84,9 +84,3 @@ jobs:
       - name: Run test
         working-directory: ./t/chaos
         run: ginkgo -r --v --progress --trace
-
-      # Debug via SSH if previous steps failed
-      - name: Set up tmate session
-        if: ${{ failure() }}
-        uses: ./.github/actions/action-tmate
-        timeout-minutes: 15

.gitmodules

@@ -1,9 +1,6 @@
 [submodule "t/toolkit"]
 	path = t/toolkit
 	url = https://github.com/api7/test-toolkit.git
-[submodule ".github/actions/action-tmate"]
-	path = .github/actions/action-tmate
-	url = https://github.com/mxschmitt/action-tmate
 [submodule "t/grpc_server_example"]
 	path = t/grpc_server_example
 	url = https://github.com/api7/grpc_server_example