Bump rexml from 3.2.5 to 3.2.8 in /tictactoe_ruby

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 to 3.2.8.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.5...v3.2.8)

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

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

tictactoe_ruby/Gemfile.lock

@@ -15,7 +15,8 @@ GEM
     rainbow (3.1.1)
     rake (13.0.6)
     regexp_parser (2.7.0)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rubocop (1.45.1)
       json (~> 2.3)
       parallel (~> 1.10)
@@ -29,10 +30,12 @@ GEM
     rubocop-ast (1.26.0)
       parser (>= 3.2.1.0)
     ruby-progressbar (1.11.0)
+    strscan (3.1.0)
     unicode-display_width (2.4.2)
 
 PLATFORMS
   x64-mingw-ucrt
+  x86_64-linux
 
 DEPENDENCIES
   minitest (~> 5.0)