Remove use of deprecated JavaConverters class

Fixes following warning:
object JavaConverters in package collection is deprecated (since 2.13.0): Use `scala.jdk.CollectionConverters` instead

Change-Id: I85b282ddd2414976d5be0f9b62648a83feeed8df

src/main/scala/com/googlesource/gerrit/plugins/analytics/common/GsonFormatter.scala

diff --git a/src/main/scala/com/googlesource/gerrit/plugins/analytics/common/GsonFormatter.scala b/src/main/scala/com/googlesource/gerrit/plugins/analytics/common/GsonFormatter.scala
index 70df461..589a70d 100644
--- a/src/main/scala/com/googlesource/gerrit/plugins/analytics/common/GsonFormatter.scala
+++ b/src/main/scala/com/googlesource/gerrit/plugins/analytics/common/GsonFormatter.scala
@@ -39,7 +39,7 @@
 
   class IterableSerializer extends JsonSerializer[Iterable[Any]] {
     override def serialize(src: Iterable[Any], typeOfSrc: Type, context: JsonSerializationContext): JsonElement = {
-      import scala.collection.JavaConverters._
+      import scala.jdk.CollectionConverters._
       context.serialize(src.asJava)
     }
   }