Merge branch 'georgekoltsov/reduce-export-batch-size-even-further' into 'master'

Lower project export batch_size even further

See merge request gitlab-org/gitlab!34714

lib/gitlab/import_export/json/streaming_serializer.rb

@@ -7,7 +7,7 @@ module Gitlab
         include Gitlab::ImportExport::CommandLineUtil
 
         BATCH_SIZE = 100
-        SMALLER_BATCH_SIZE = 20
+        SMALLER_BATCH_SIZE = 2
 
         def self.batch_size(exportable)
           if Feature.enabled?(:export_reduce_relation_batch_size, exportable)