doc: Clarify the destination of checkout, remove investigative steps

.forgejo/workflows/continuous-integration.yaml

@@ -20,14 +20,10 @@ jobs:
         # it wouldn't be recognized anyway)
         working-directory: app-proto
     steps:
-      # check out the repository to the workspace directory. in the action
-      # description, you can get and set the workspace directory through the
-      # `github.workspace` and `env.GITHUB_WORKSPACE` labels, which always have
-      # the same value. in the container, you can get the workspace directory
-      # from the `GITHUB_WORKSPACE` environment variable
+      # Check out the repository so that its top-level directory is the
+      # workspace directory (action variable `github.workspace`, environment
+      # variable `$GITHUB_WORKSPACE`):
       - uses: https://code.forgejo.org/actions/checkout@v4
       
       - uses: ./.forgejo/setup-trunk
-      - run: echo $GITHUB_WORKSPACE
-      - run: ls ..
       - run: RUSTFLAGS='-D warnings' cargo test