string.c: [DOC] Fix a typo in String#dump

[Fix GH-1531][ci skip]
Author:    Alex Semyonov <alex@semyonov.us>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57802 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -5787,7 +5787,7 @@ rb_str_inspect(VALUE str)
  *  Produces a version of +str+ with all non-printing characters replaced by
  *  <code>\nnn</code> notation and all special characters escaped.
  *
- *    "hello \n ''".dump  #=> "\"hello \\n ''\"
+ *    "hello \n ''".dump  #=> "\"hello \\n ''\""
  */
 
 VALUE