ci(pre-commit): finalise `rstcheck` configuration [skip ci]

* Automated using https://github.com/myii/ssf-formula/pull/267

.pre-commit-config.yaml

@@ -52,4 +52,5 @@ repos:
     hooks:
       - id: rstcheck
         name: Check reST files using rstcheck
+        exclude: 'docs/CHANGELOG.rst'
         args: [--report=warning]