tests: relax the "version text" length check, accept longer strings

tests: relax the "version text" length check, accept longer strings

The version text length check fails for git setups that use more digits
in abbreviated hashes, as is recommended by e.g. the Linux kernel project.

Raise the upper limit for acceptable version strings, and add comments
on how the limits were determined. The test still might fail in setups
of slightly different configuration, but now it's easier to see why the
test failed, and how to adjust the test.

Signed-off-by: Gerhard Sittig <redacted>