struct.c: [DOC] improve docs for Struct.new

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61232 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

struct.c

@@ -475,11 +475,10 @@ rb_struct_define_under(VALUE outer, const char *name, ...)
  *     Customer.new("Dave", "123 Main")
  *     #=> #<struct Customer name="Dave", address="123 Main">
  *
- *  If keyword_init: true option is given, .new takes keyword arguments instead
- *  of normal arguments.
+ *  If the optional +keyword_init+ keyword argument is set to +true+,
+ *  .new takes keyword arguments instead of normal arguments.
  *
  *     Customer = Struct.new(:name, :address, keyword_init: true)
- *     #=> Customer
  *     Customer.new(name: "Dave", address: "123 Main")
  *     #=> #<struct Customer name="Dave", address="123 Main">
  *