chore: bump rexml from 3.2.7 to 3.3.6 in /docs (#1122)

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.7 to 3.3.6.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.7...v3.3.6)

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

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

docs/Gemfile.lock

@@ -13,6 +13,7 @@ GEM
       faraday-net_http (~> 2.0)
       ruby2_keywords (>= 0.0.4)
     faraday-net_http (2.0.3)
+    ffi (1.15.5)
     ffi (1.15.5-x64-mingw-ucrt)
     forwardable-extended (2.6.0)
     http_parser.rb (0.8.0)
@@ -64,7 +65,8 @@ GEM
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.7)
+    rexml (3.3.6)
+      strscan
     rouge (3.29.0)
     ruby2_keywords (0.0.5)
     safe_yaml (1.0.5)
@@ -73,6 +75,7 @@ GEM
     sawyer (0.9.2)
       addressable (>= 2.3.5)
       faraday (>= 0.17.3, < 3)
+    strscan (3.1.0)
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
     tzinfo (2.0.4)
@@ -84,6 +87,7 @@ GEM
 
 PLATFORMS
   x64-mingw-ucrt
+  x86_64-linux
 
 DEPENDENCIES
   jekyll (~> 4.2, >= 4.2.2)