Fixed rdoc style

hsbt · hsbt · commit 35c18fe5293f · 2018-03-22T11:10:29.000+09:00
diff --git a/History.rdoc b/History.rdoc
@@ -5,7 +5,7 @@
 * Bump `required_ruby_version` to Ruby 2.0.0. Rake has already
   removed support for Ruby 1.9.x.
 
-=== Enhancements:
+==== Enhancements:
 
 * Support `test-bundled-gems` task on ruby core.
 
