Bump rexml from 3.2.5 to 3.2.8

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 to 3.2.8.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.5...v3.2.8)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    recipient_interceptor (0.3.0)
+    recipient_interceptor (0.3.1)
       mail
 
 GEM
@@ -18,7 +18,8 @@ GEM
     rainbow (3.0.0)
     rake (12.3.3)
     regexp_parser (2.0.3)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.9.0)
       rspec-core (~> 3.9.0)
       rspec-expectations (~> 3.9.0)
@@ -50,6 +51,7 @@ GEM
     standard (0.13.0)
       rubocop (= 1.10.0)
       rubocop-performance (= 1.9.2)
+    strscan (3.1.0)
     unicode-display_width (2.0.0)
 
 PLATFORMS