Fold clang-format into the lint dependency group

clang-format checks python/dolfinx/wrappers (nanobind C++ bindings),
which live under python/, so it belongs alongside ruff and gersemi in
the lint group rather than as a separate ad hoc install in CI.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: jhale

.github/workflows/ccpp.yml

@@ -40,7 +40,7 @@ jobs:
         run: cat .github/workflows/fenicsx-refs.env >> $GITHUB_ENV
 
       - name: Install linting tools
-        run: pip install --group python/pyproject.toml:lint clang-format
+        run: pip install --group python/pyproject.toml:lint
       - name: ruff .py files in C++ code
         run: |
           cd cpp/

python/pyproject.toml

@@ -73,7 +73,7 @@ docs = [
       "sphinxcontrib-bibtex",
       "fenics-dolfinx[demo]",
 ]
-lint = ["ruff", "gersemi"]
+lint = ["ruff", "gersemi", "clang-format"]
 ci = [
       "pytest-xdist",
       "mypy",