adoc links point to the raw format which is illegible; point to the repo instead

[mub]

The provided links to the getting-started-macros repo point to the raw format which is unformatted plain text. Link like this instead:

https://github.com/spring-guides/getting-started-macros/blob/master/prereq_editor_jdk_buildtools.adoc

↑ that would provide a →formatted view.

[gregturn]

Perhaps on GitHub, but not on spring.io.

[mub]

The link I proposed should work from any site.

[gregturn]

Didn't work. I tried to make that tweak, in case things had changed (fdb2bdd).

A) The fragment is located elsewhere, hence github's security policies won't render it here, still leaving you with a link.

B) It failed to render itself as expected.

[gregturn]

So I reverted it to as it was before.