Bump rexml from 3.2.6 to 3.3.9 (#821)

Author: spencertransier

Gemfile.lock

@@ -309,7 +309,7 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.2.6)
+    rexml (3.3.9)
     rouge (2.0.7)
     rubocop (1.60.2)
       json (~> 2.3)
@@ -356,13 +356,13 @@ GEM
     uber (0.1.0)
     unicode-display_width (2.5.0)
     word_wrap (1.0.0)
-    xcodeproj (1.24.0)
+    xcodeproj (1.25.1)
       CFPropertyList (>= 2.3.3, < 4.0)
       atomos (~> 0.1.3)
       claide (>= 1.0.2, < 2.0)
       colored2 (~> 3.1)
       nanaimo (~> 0.3.0)
-      rexml (~> 3.2.4)
+      rexml (>= 3.3.6, < 4.0)
     xcpretty (0.3.0)
       rouge (~> 2.0.7)
     xcpretty-travis-formatter (1.0.1)