Bump rexml from 3.3.6 to 3.3.9 in /.github/actions/notices_generation (firebase#13981)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

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)