Bump kramdown from 2.4.0 to 2.5.1 (#4497)

* Bump kramdown from 2.4.0 to 2.5.1

Bumps [kramdown](https://github.com/gettalong/kramdown) from 2.4.0 to 2.5.1.
- [Release notes](https://github.com/gettalong/kramdown/releases)
- [Changelog](https://github.com/gettalong/kramdown/blob/master/doc/news.page)
- [Commits](https://github.com/gettalong/kramdown/commits)

---
updated-dependencies:
- dependency-name: kramdown
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

* adapted accessible footnotes test to add role=doc-noteref - it looks like Kramdown's output required the test to include role=doc-noteref to validate accessible HTML

---------

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

Gemfile.lock

@@ -352,8 +352,8 @@ GEM
     kaminari-core (1.2.2)
     knapsack (4.0.0)
       rake
-    kramdown (2.4.0)
-      rexml
+    kramdown (2.5.1)
+      rexml (>= 3.3.9)
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
     language_server-protocol (3.17.0.3)
@@ -495,8 +495,7 @@ GEM
     request_store_rails (2.0.0)
       concurrent-ruby (~> 1.0)
     retriable (3.1.2)
-    rexml (3.3.3)
-      strscan
+    rexml (3.4.0)
     rinku (2.0.6)
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
@@ -606,7 +605,6 @@ GEM
       spring (>= 4)
     stoplight (3.0.2)
       redlock (~> 1.0)
-    strscan (3.1.2)
     text (1.3.1)
     thor (1.3.2)
     timeliness (0.4.5)

spec/requests/accessible_footnotes_spec.rb

@@ -8,8 +8,8 @@
   subject { response.body }
 
   it "makes footnotes accessible" do
-    is_expected.to include(%(<a href="#fn:1" class="footnote" rel="footnote"><span class="visually-hidden">Footnote </span>1</a>))
-    is_expected.to include(%(<a href="#fn:2" class="footnote" rel="footnote"><span class="visually-hidden">Footnote </span>2</a>))
+    is_expected.to include(%(<a href="#fn:1" class="footnote" rel="footnote" role="doc-noteref"><span class="visually-hidden">Footnote </span>1</a>))
+    is_expected.to include(%(<a href="#fn:2" class="footnote" rel="footnote" role="doc-noteref"><span class="visually-hidden">Footnote </span>2</a>))
 
     is_expected.to include(%(<a href="#fnref:1" class="reversefootnote" role="doc-backlink"><span class="visually-hidden">Location of footnote 1</span>↩</a>))
     is_expected.to include(%(<a href="#fnref:2" class="reversefootnote" role="doc-backlink"><span class="visually-hidden">Location of footnote 2</span>↩</a>))