do guava updates in one group

Author: cdietrich

.github/dependabot.yml

@@ -10,4 +10,8 @@ updates:
       interval: "daily"
     allow:
       - dependency-name: "io.github.classgraph:classgraph"
-      - dependency-name: "com.google.guava:*"
+      - dependency-name: "com.google.guava:*"
+    groups:
+      guava-updates:
+        patterns:
+          - "com.google.guava:*"