ci: leave C formatting to pre-commit

.gitlab-ci.yml

@@ -43,12 +43,8 @@ Check style:
   variables:
     STYLE_PATCH: ${CI_PROJECT_DIR}/style.patch
   before_script:
-    - apk add clang-extra-tools git pre-commit python3
+    - apk add git pre-commit
   script:
-    # Exclude the automatically generated mtime_iso8601.c:
-    - c_cxx_files=$(find "${CI_PROJECT_DIR}" -name 'mtime_iso8601.c' -prune -o \( -name '*.h' -o -name '*.c' \) -print)
-    - clang-format --style=file -i ${c_cxx_files}
-
     - pre-commit run --color=always --all-files
 
     - git -C "${CI_PROJECT_DIR}" diff --patch-with-raw > "${STYLE_PATCH}"