Disable vulnerability reports

Reason: They do not work and this breaks grouping!
Also these updates prevent updating to the latest version and use dependabot's "fix" version instead.

Example:
* xdev-software/spring-data-eclipse-store#358
* xdev-software/spring-data-eclipse-store#349

Author: AB-xdev

self-hosted.json5

@@ -13,5 +13,8 @@
       "concurrentRequestLimit": 500,
       "maxRequestsPerSecond": 200
     }
-  ]
+  ],
+  "vulnerabilityAlerts": {
+    "enabled": false
+  }
 }