bump all examples/ gradle wrapper version to 6.3

[paulvi]

ref #46

1 gradle download should be enough

[nschwermann]

My current PR updates wrapper to 6.8 #61

[paulvi]

OK, whichever gets merged first,

there should not be 3 gradle versions in one project

[nschwermann]

Hmm, okay. In the meantime you don't need to use the wrapper at all you can use gradle instead of ./gradlew

[paulvi]

Thanks, I know

Well, with the pace of gradle changes, global gradle can do only maybe for the same major version

And IDEA bundles its own gradle version (7.1 as of now), in the end that leads to unclear situation, like what exact gradle instance is running

[paulvi]

resolved with #61