RFR: 8254100: FX: Update copyright year in docs, readme files to 2021

[Jeanette Winzenburg]

On Thu, 22 Oct 2020 12:58:09 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> just curious - why 2021? back to the future or do we already prepare for the next release?
>
> The latter. JavaFX 16 will ship in March 2021. Note that this doesn't touch the "last modified" year in the copyright license header of those files, but rather the copyright year that will appear in the API docs when running `gradle javadoc`. We did the same thing last October, updating the copyright year for docs to 2020. See [JDK-8232522](https://bugs.openjdk.java.net/browse/JDK-8232522).

thanks :)

-------------

PR: https://git.openjdk.java.net/jfx/pull/330