[ruby/uri] [DOC] Fix result of sample code in #user=

A `password` is cleared when change a user now.

https://github.com/ruby/uri/commit/af6714473c

lib/uri/generic.rb

@@ -466,7 +466,7 @@ module URI
     #
     #   uri = URI.parse("http://john:S3nsit1ve@my.example.com")
     #   uri.user = "sam"
-    #   uri.to_s  #=> "http://sam:V3ry_S3nsit1ve@my.example.com"
+    #   uri.to_s  #=> "http://sam@my.example.com"
     #
     def user=(user)
       check_user(user)