Bump rexml from 3.2.8 to 3.3.9 in /legacy

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.8 to 3.3.9.
- [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...v3.3.9)

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

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

legacy/Gemfile.lock

@@ -151,8 +151,7 @@ GEM
     rainbow (3.1.1)
     rake (13.0.6)
     regexp_parser (2.6.2)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.9)
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
       rspec-expectations (~> 3.12.0)
@@ -189,7 +188,6 @@ GEM
     semantic_puppet (1.0.4)
     singleton (0.1.1)
     spdx-licenses (1.3.0)
-    strscan (3.1.0)
     text (1.3.1)
     thor (1.2.1)
     trollop (2.9.10)