chore(deps): bump alpine from 3.18 to 3.19 in /hack/api-docs

Bumps alpine from 3.18 to 3.19.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Signed-off-by: Moritz Johner <beller.moritz@googlemail.com>

hack/api-docs/Dockerfile

@@ -11,12 +11,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM alpine:3.18@sha256:34871e7290500828b39e22294660bee86d966bc0017544e848dd9a255cdf59e0
+FROM alpine:3.19@sha256:51b67269f354137895d43f3b3d810bfacd3945438e94dc5ac55fdac340352f48
 COPY requirements.txt /
 RUN apk add -U --no-cache \
     python3 \
     python3-dev \
-    py3-pip==23.1.2-r0 \
+    py3-pip \
     musl-dev \
     git \
     openssh \