chore: combine golang version rules into single config

On-behalf-of: Gerald Morrison (SAP) <gerald.morrison@sap.com>
Signed-off-by: Gerald Morrison (SAP) <gerald.morrison@sap.com>

Author: morrison-sap

.github/renovate.json5

@@ -33,17 +33,11 @@
       automerge: true,
     },
     {
-      description: "Group golang versions (go directive from go.mod)",
+      description: "Group golang versions (go directive + Docker images)",
       matchDatasources: ["golang-version"],
-      rangeStrategy: "bump",
-      groupName: "Golang versions",
-      groupSlug: "golang-versions",
-      minimumReleaseAge: null,
-    },
-    {
-      description: "Group golang Docker image updates",
       matchManagers: ["dockerfile"],
       matchPackageNames: ["golang"],
+      rangeStrategy: "bump",
       groupName: "Golang versions",
       groupSlug: "golang-versions",
       minimumReleaseAge: null,