Merge pull request #257 from ruby-syntax-tree/dependabot/bundler/kramdown-2.5.2

Bump kramdown from 2.5.1 to 2.5.2

Author: github-actions[bot]

Gemfile.lock

@@ -1,12 +1,12 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    kramdown (2.5.1)
-      rexml (>= 3.3.9)
+    kramdown (2.5.2)
+      rexml (>= 3.4.4)
     power_assert (3.0.1)
     prettier_print (1.2.1)
     rake (13.3.1)
-    rexml (3.3.9)
+    rexml (3.4.4)
     rouge (4.7.0)
     syntax_tree (6.3.0)
       prettier_print (>= 1.2.0)