Merge pull request #251 from ruby-syntax-tree/dependabot/bundler/test-unit-3.7.3

Bump test-unit from 3.7.1 to 3.7.3

Author: github-actions[bot]

Gemfile.lock

@@ -3,14 +3,14 @@ GEM
   specs:
     kramdown (2.5.1)
       rexml (>= 3.3.9)
-    power_assert (3.0.0)
+    power_assert (3.0.1)
     prettier_print (1.2.1)
     rake (13.3.1)
     rexml (3.3.9)
     rouge (4.6.1)
     syntax_tree (6.3.0)
       prettier_print (>= 1.2.0)
-    test-unit (3.7.1)
+    test-unit (3.7.3)
       power_assert
 
 PLATFORMS