true,false: remove unnecessary newline from version string

[cakebaker]

This PR removes an unnecessary newline from the version strings of true and false.

Before change:

$ cargo run -q false --version
false 0.0.30

$

After change:

$ cargo run -q false --version
false 0.0.30
$

The PR also makes some minor improvements to the tests of true and false.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)