chore(deps): Bump rexml from 3.3.6 to 3.3.9

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.6 to 3.3.9.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.3.6...v3.3.9)

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

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

Gemfile.lock

@@ -188,8 +188,7 @@ GEM
     regexp_parser (2.9.2)
     reline (0.5.10)
       io-console (~> 0.5)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rgl (0.6.6)
       pairing_heap (>= 0.3, < 4.0)
       rexml (~> 3.2, >= 3.2.4)
@@ -219,7 +218,6 @@ GEM
     servolux (0.13.0)
     stream (0.5.5)
     stringio (3.1.1)
-    strscan (3.1.0)
     sysexits (1.2.0)
     temple (0.10.3)
     terser (1.1.20)