string.c: minor grammar fix [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53509 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Mon Jan 12 18:34:34 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* string.c: minor grammar fix [ci skip]
+
 Mon Jan 12 16:09:09 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* test/ruby/enc/test_casing_options.rb: Tests for option

string.c

@@ -8600,7 +8600,7 @@ rb_str_b(VALUE str)
  *  call-seq:
  *     str.valid_encoding?  -> true or false
  *
- *  Returns true for a string which encoded correctly.
+ *  Returns true for a string which is encoded correctly.
  *
  *    "\xc2\xa1".force_encoding("UTF-8").valid_encoding?  #=> true
  *    "\xc2".force_encoding("UTF-8").valid_encoding?      #=> false