chore(deps): bump rexml from 3.2.8 to 3.3.6 in /mobile/ios

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.8 to 3.3.6.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](https://github.com/ruby/rexml/compare/v3.2.8...v3.3.6)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

mobile/ios/Gemfile.lock

@@ -169,8 +169,8 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.6)
+      strscan
     rouge (2.0.7)
     ruby2_keywords (0.0.5)
     rubyzip (2.3.2)
@@ -195,13 +195,13 @@ GEM
     uber (0.1.0)
     unicode-display_width (1.8.0)
     word_wrap (1.0.0)
-    xcodeproj (1.24.0)
+    xcodeproj (1.25.0)
       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 (>= 3.3.2, < 4.0)
     xcpretty (0.3.0)
       rouge (~> 2.0.7)
     xcpretty-travis-formatter (1.0.1)