doc: improve buffer examples

This switches the order of the print statements. In most docs we have them below so it is clear that it is "output" while other things are above to describe what is triggered.

It is also easier to group output that way.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

docs