chore(deps): update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/_tests.yaml

@@ -71,7 +71,7 @@ jobs:
             matrix.python-version == '3.14' &&
             env.CODECOV_TOKEN != ''
           }}
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
@@ -128,7 +128,7 @@ jobs:
             matrix.python-version == '3.14' &&
             env.CODECOV_TOKEN != ''
           }}
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with: