refactor: Bump rexml from 3.3.3 to 3.3.6 (#1800)

Author: dependabot[bot]

Gemfile.lock

@@ -92,7 +92,7 @@ GEM
     public_suffix (4.0.7)
     rake (13.0.6)
     redcarpet (3.6.0)
-    rexml (3.3.3)
+    rexml (3.3.6)
       strscan
     rouge (2.0.7)
     ruby-macho (1.4.0)