error.c: [DOC] fix typo [ci skip]

* error.c (RuntimeError): example code uses Kernel#raise instance
  method, not Kernel.raise singleton method.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60185 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

error.c

@@ -2016,7 +2016,7 @@ syserr_eqq(VALUE self, VALUE exc)
  *
  *     RuntimeError: can't modify frozen Array
  *
- *  Kernel.raise will raise a RuntimeError if no Exception class is
+ *  Kernel#raise will raise a RuntimeError if no Exception class is
  *  specified.
  *
  *     raise "ouch"