Workbench: Flexible Pip contraints.

The OS packages come with a version of packaging. Installing a different
version with Pip is not possible as it requires uninstalling the OS
version which doesn't have all of the needed metadata, therefore the Pip
constraint. Instead of updating the contraint manually everytime it's
updated in Debian, use the version that's currently installed and it
should always be OK (hopefully).

workbench/Dockerfile

@@ -176,7 +176,7 @@ ENV PIPX_HOME /opt/pipx
 ENV PIPX_BIN_DIR /opt/pipx/bin
 # hadolint ignore=DL3013
 RUN export PIP_CONSTRAINT=/tmp/constraint.txt && \
-    echo 'packaging==24.1' >> "$PIP_CONSTRAINT" && \
+    python3 -m pip freeze | grep packaging >> "$PIP_CONSTRAINT" && \
     python3 -m pip install --no-cache-dir --break-system-packages \
         Glances \
         PyGObject \