Update version, URL in serverless

docs/serverless/rules/rules-coverage.mdx

@@ -16,7 +16,7 @@ Mirroring the MITRE ATT&CK® framework, columns represent major tactics, and cel
 
 <DocCallOut title="Note">
 
-This page only includes the detection rules you currently have installed, and only rules that are mapped to MITRE ATT&CK®. The coverage page maps detections to the following [MITRE ATT&CK® version](https://attack.mitre.org/resources/updates/updates-october-2023) used by ((elastic-sec)): `v14.1`. Elastic prebuilt rules that aren't installed and custom rules that are either unmapped or mapped to a deprecated tactic or technique will not appear on the coverage map.
+This page only includes the detection rules you currently have installed, and only rules that are mapped to MITRE ATT&CK®. The coverage page maps detections to the following [MITRE ATT&CK® version](https://attack.mitre.org/resources/updates/updates-april-2024) used by ((elastic-sec)): `v15.1`. Elastic prebuilt rules that aren't installed and custom rules that are either unmapped or mapped to a deprecated tactic or technique will not appear on the coverage map.
 
 You can map custom rules to tactics in **Advanced settings** when creating or editing a rule.