chore(deps): update actions/setup-python action to v6 (#63)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
         run: |
           ${GITHUB_WORKSPACE}/vim-themis/bin/themis --reporter dot
       - name: setup python
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
         with:
           python-version: '3.13'
       - name: collect coverage