Bump rexml from 3.2.8 to 3.3.3 in /example (#604)

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.8 to 3.3.3.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.8...v3.3.3)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

example/Gemfile.lock

@@ -75,21 +75,21 @@ GEM
     netrc (0.11.0)
     nkf (0.2.0)
     public_suffix (4.0.7)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.3)
+      strscan
     ruby-macho (2.5.1)
     strscan (3.1.0)
     typhoeus (1.4.1)
       ethon (>= 0.9.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    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)
 
 PLATFORMS
   ruby