Bump rexml from 3.3.6 to 3.3.9 in /.github/actions/notices_generation

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] <[email protected]>

Author: dependabot[bot]

.github/actions/notices_generation/Gemfile.lock

@@ -79,14 +79,12 @@ GEM
       sawyer (~> 0.8.0, >= 0.5.3)
     plist (3.6.0)
     public_suffix (4.0.6)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     ruby-macho (2.5.1)
     ruby2_keywords (0.0.2)
     sawyer (0.8.2)
       addressable (>= 2.3.5)
       faraday (> 0.8, < 2.0)
-    strscan (3.1.0)
     typhoeus (1.4.1)
       ethon (>= 0.9.0)
     tzinfo (2.0.6)