Update dependency rexml to v3.4.1

Author: renovate[bot]

Gemfile.lock

@@ -87,7 +87,7 @@ GEM
     netrc (0.11.0)
     nkf (0.2.0)
     public_suffix (4.0.7)
-    rexml (3.4.0)
+    rexml (3.4.1)
     ruby-macho (2.5.1)
     securerandom (0.3.2)
     typhoeus (1.4.1)