Downgrade rexml to v3.2.8

The version of `rexml` in `Gemfile.lock` has been downgraded from 3.3.9 to 3.2.8, and the dependency constraint for `xcodeproj` was adjusted from `~> 3.3.9` to `~> 3.2.4`.

Author: eby-dev

Gemfile.lock

@@ -179,7 +179,7 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.3.9)
+    rexml (3.2.8)
       strscan (>= 3.0.9)
     rouge (2.0.7)
     ruby2_keywords (0.0.5)
@@ -211,7 +211,7 @@ GEM
       claide (>= 1.0.2, < 2.0)
       colored2 (~> 3.1)
       nanaimo (~> 0.3.0)
-      rexml (~> 3.3.9)
+      rexml (~> 3.2.4)
     xcpretty (0.3.0)
       rouge (~> 2.0.7)
     xcpretty-travis-formatter (1.0.1)