* Relicense Shrine demo to match rest of repository

The Shrine demo was Apache-licensed. The code was mostly
Google-written, with contributions from:

 - Michelle Dudley (@michdud)

 - Abhijeeth Padarthi <rkinabhi@gmail.com> (@rkinabhi)

 - @a14n

I contacted all three, and they confirmed their approval for this
change, as described below.

Abhijeeth Padarthi said by e-mail on Thu, Nov 21, 2019 at 5:48 PM:

> hi Ian,
>
> sure :)
>
> let me know if I need to do anything on my end..

Michelle Dudley wrote by e-mail on Sun, Nov 24, 2019 at 2:07 PM:

> Hi Ian,
>
> That would be ok with me.
>
> Thanks,
>
> Michelle

@a14n said on Discord's Flutter server in the #hackers channel at 10:44PM on Thursday, November 21, 2019:

> @Hixie no problem I agree with this relicensing

* Remove shrine loophole from license checker.