RFR: 8231668: Remove ForceDynamicNumberOfGCThreads

[Aditya Mandaleeka]

Thanks Aleksey and Thomas for reviewing. I've updated the patch with the feedback. I left the
TestDynamicNumberofGCThreads test in place but fixed the comment. Seems like it's worth revisiting
that test to make it more useful as a separate issue.

Aleksey, I am coming from the Git world and still getting familiar with the workflow here. I hadn't
heard of the MqExtension until your mail, but I tried it out. To be honest, I was quite confused
about how to use it in conjunction with the webrev script even after reading some documentation. I
ended up with a webrev which appears to have the right code diff, but I'm not sure if all the
metadata is in the form you'd expect. I'd appreciate it if you could verify that.

Updated webrev is at: https://cr.openjdk.java.net/~adityam/8231668/webrev.01/

Severin Gehwolf wrote: 
> For authors, 'Contributed-by:' line would not be necessary, no? They
> could just use "hg commit -u <census-user>". That's my understanding
> anyhow.

This matches my understanding as well from reading http://openjdk.java.net/projects/#project-author.
That said, I don't really have a strong preference on it, so whatever you all prefer is fine with
me. Just let me know what I need to do!

Thanks,
Aditya