Revert a change removed a needed monger require [ci drivers]

This is needed for Mongo tests to work

src/metabase/driver/mongo/query_processor.clj

@@ -24,6 +24,14 @@
            org.bson.types.ObjectId
            org.joda.time.DateTime))
 
+;; See http://clojuremongodb.info/articles/integration.html
+;; Loading these namespaces will load appropriate Monger integrations with JODA Time and Cheshire respectively
+;;
+;; These are loaded here and not in the `:require` above because they tend to get automatically removed by
+;; `cljr-clean-ns` and also cause Eastwood to complain about unused namespaces
+(require 'monger.joda-time
+         'monger.json)
+
 (def ^:private ^:const $subtract :$subtract)