Bump rexml from 3.2.6 to 3.2.8

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.6 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@v3.2.6...v3.2.8)

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

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

Gemfile.lock

@@ -111,7 +111,8 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rgl (0.6.6)
       pairing_heap (>= 0.3, < 4.0)
       rexml (~> 3.2, >= 3.2.4)
@@ -120,6 +121,7 @@ GEM
       ffi (~> 1.9)
     servolux (0.13.0)
     stream (0.5.5)
+    strscan (3.1.0)
     temple (0.10.3)
     terser (1.2.2)
       execjs (>= 0.3.0, < 3)