gha: dco: small tweaks to running the container

- add `--quiet` to suppress pull progress output
- use `./` instead of `$(pwd)` now that relative paths are supported
- set the working directory on the container, so that we don't have to `cd`

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 9a14299540)
Signed-off-by: Austin Vazquez <macedonv@amazon.com>

.github/workflows/.dco.yml

@@ -49,10 +49,12 @@ jobs:
         name: Validate
         run: |
           docker run --rm \
-            -v "$(pwd):/workspace" \
+            --quiet \
+            -v ./:/workspace \
+            -w /workspace \
             -e VALIDATE_REPO \
             -e VALIDATE_BRANCH \
-            alpine:${{ env.ALPINE_VERSION }} sh -c 'apk add --no-cache -q bash git openssh-client && git config --system --add safe.directory /workspace && cd /workspace && hack/validate/dco'
+            alpine:${{ env.ALPINE_VERSION }} sh -c 'apk add --no-cache -q bash git openssh-client && git config --system --add safe.directory /workspace && hack/validate/dco'
         env:
           VALIDATE_REPO: ${{ github.server_url }}/${{ github.repository }}.git
           VALIDATE_BRANCH: ${{ steps.base-ref.outputs.result }}