Revise sentence case heading rule

[jdbaldry]

Lots of false positives in https://github.com/grafana/website/pull/19378

{"message": "[Grafana.Headings] Use sentence-style capitalization for 'DNS check'. If your heading contains capitalized words that represent product names, you need to add those words as exceptions in https://github.com/grafana/writers-toolkit/blob/main/vale/Grafana/Headings.yml for them to be considered correctly cased. Vale considers multi-word exceptions such as _Grafana Enterprise Metrics_ as a single correctly cased word. \n\nFor more information, refer to https://developers.google.com/style/capitalization#capitalization-in-titles-and-headings.\n\nIf the rule is incorrect or needs improving, [report an issue](https://github.com/grafana/writers-toolkit/issues/new?title=Grafana.Headings%20%3A%20%3CISSUE%3E).\n\nIf you have reason to diverge from the style guidance, to skip a rule, refer to [Skip rules](https://grafana.com/docs/writers-toolkit/review/lint-prose/#skip-rules).", "location": {"path": "content/docs/grafana-cloud/monitor-public-endpoints/create-checks/checks/dns.md", "range": {"start": {"line": 11, "column": 3}}}, "severity": "WARNING"}
{"message": "[Grafana.Headings] Use sentence-style capitalization for 'TCP check'. If your heading contains capitalized words that represent product names, you need to add those words as exceptions in https://github.com/grafana/writers-toolkit/blob/main/vale/Grafana/Headings.yml for them to be considered correctly cased. Vale considers multi-word exceptions such as _Grafana Enterprise Metrics_ as a single correctly cased word. \n\nFor more information, refer to https://developers.google.com/style/capitalization#capitalization-in-titles-and-headings.\n\nIf the rule is incorrect or needs improving, [report an issue](https://github.com/grafana/writers-toolkit/issues/new?title=Grafana.Headings%20%3A%20%3CISSUE%3E).\n\nIf you have reason to diverge from the style guidance, to skip a rule, refer to [Skip rules](https://grafana.com/docs/writers-toolkit/review/lint-prose/#skip-rules).", "location": {"path": "content/docs/grafana-cloud/monitor-public-endpoints/create-checks/checks/tcp.md", "range": {"start": {"line": 11, "column": 3}}}, "severity": "WARNING"}
{"message": "[Grafana.Headings] Use sentence-style capitalization for 'MultiHTTP check'. If your heading contains capitalized words that represent product names, you need to add those words as exceptions in https://github.com/grafana/writers-toolkit/blob/main/vale/Grafana/Headings.yml for them to be considered correctly cased. Vale considers multi-word exceptions such as _Grafana Enterprise Metrics_ as a single correctly cased word. \n\nFor more information, refer to https://developers.google.com/style/capitalization#capitalization-in-titles-and-headings.\n\nIf the rule is incorrect or needs improving, [report an issue](https://github.com/grafana/writers-toolkit/issues/new?title=Grafana.Headings%20%3A%20%3CISSUE%3E).\n\nIf you have reason to diverge from the style guidance, to skip a rule, refer to [Skip rules](https://grafana.com/docs/writers-toolkit/review/lint-prose/#skip-rules).", "location": {"path": "content/docs/grafana-cloud/monitor-public-endpoints/create-checks/checks/multihttp.md", "range": {"start": {"line": 11, "column": 3}}}, "severity": "WARNING"}