Update pre-commit hook gitleaks/gitleaks to v8.21.0 (#874)

| datasource  | package           | from    | to      |
| ----------- | ----------------- | ------- | ------- |
| github-tags | gitleaks/gitleaks | v8.19.3 | v8.21.0 |

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

Author: renovate[bot]

.pre-commit-config.yaml

@@ -31,7 +31,7 @@ repos:
       - id: golangci-lint-full
 
   - repo: https://github.com/gitleaks/gitleaks
-    rev: v8.19.3
+    rev: v8.21.0
     hooks:
       - id: gitleaks