Update dependency parallel to v2

Author: renovate[bot]

Gemfile.lock

@@ -429,7 +429,7 @@ GEM
     optimist (3.1.0)
     orm_adapter (0.5.0)
     ostruct (0.6.3)
-    parallel (1.28.0)
+    parallel (2.1.0)
     parser (3.3.11.1)
       ast (~> 2.4.1)
       racc