Workbench: Avoid Cython 3.

It breaks the installation of older PyYAML versions.

workbench/Dockerfile

@@ -158,6 +158,7 @@ RUN apt-get update && \
     locale-gen && \
     export PIP_CONSTRAINT=/tmp/constraint.txt && \
     echo 'resolvelib==0.5.4' > "$PIP_CONSTRAINT" && \
+    echo 'Cython < 3.0' >> "$PIP_CONSTRAINT" && \
     python3 -m pip install --no-cache-dir --break-system-packages \
         https://github.com/aws/aws-cli/archive/refs/heads/v2.zip \
         Glances \