Bump rexml from 3.3.3 to 3.3.9 in /rabbitmq

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.3 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@v3.3.3...v3.3.9)

---
updated-dependencies:
- dependency-name: rexml
  dependency-version: 3.3.9
  dependency-type: indirect
...

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

Author: dependabot[bot]

rabbitmq/Gemfile.lock

@@ -36,8 +36,7 @@ GEM
     rake (13.0.6)
     rbtree (0.4.6)
     regexp_parser (2.8.0)
-    rexml (3.3.3)
-      strscan
+    rexml (3.3.9)
     rubocop (1.50.2)
       json (~> 2.3)
       parallel (~> 1.10)
@@ -69,7 +68,6 @@ GEM
     standard-performance (1.0.1)
       lint_roller (~> 1.0)
       rubocop-performance (~> 1.16.0)
-    strscan (3.1.0)
     unicode-display_width (2.4.2)
 
 PLATFORMS