Fix linting image build failure due to PEP 668

Pip had a check enabled that fails the install due to packages being
managed by the OS.
The added flag ignores this check.

Otherwise, the build fails with:
```
11.85 × This environment is externally managed
11.85 ╰─>
11.85     The system-wide python installation should be maintained using the
11.85     system package manager (apk) only.
...
11.85 note: If you believe this is a mistake, please contact your Python
  installation or OS distribution provider. You can override this, at the risk
  of breaking your Python installation or OS, by passing
  --break-system-packages.
11.85 hint: See PEP 668 for the detailed specification.
```

Signed-off-by: Mike Kolesnik <[email protected]>

package/Dockerfile.shipyard-linting

@@ -29,7 +29,7 @@ ENV MARKDOWNLINT_VERSION=0.33.0 \
 RUN apk add --no-cache bash findutils git grep make nodejs py3-six shellcheck upx yamllint yq && \
     apk add --no-cache --virtual installers npm py3-pip && \
     npm install -g markdownlint-cli@${MARKDOWNLINT_VERSION} && \
-    pip install gitlint==${GITLINT_VERSION} && \
+    pip install --break-system-packages gitlint==${GITLINT_VERSION} && \
     find /usr/bin/ -type f -executable -newercc /proc -size +1M  \( -execdir upx {} \; -o -true \) && \
     find /usr/lib/ -name __pycache__ -type d -exec rm -rf {} + && \
     apk del installers