Revert "mach: switch to uv for managing python venv (#34504)" (#34548)

This reverts commit 4103421ba5.

Signed-off-by: Mukilan Thiyagarajan <mukilan@igalia.com>

.github/actions/setup-python/action.yml

@@ -1,20 +0,0 @@
-name: Setup Python and uv
-inputs:
-  skip-python-setup:
-    required: false
-    description: "Whether to skip installing python using Github's `setup-python` action"
-    default: false
-runs:
-  using: "composite"
-  steps:
-    # Use the setup-python action to take advantage of the cache. uv will
-    # symlink to this version.
-    - name: Setup system python
-      if: ${{ inputs.skip-python-setup != 'true' }}
-      uses: actions/setup-python@v5
-      with:
-        python-version-file: '.python-version'
-    - name: Install uv
-      uses: astral-sh/setup-uv@v4
-      with:
-        version: "0.5.6"