run_test_file() duration longer than 1min are incorrectly displayed

[katrinabrock]

print.tinytest expects duration attribute of output object to be in seconds. However, run_test_file produces a difftime object with "auto" units.

Issue is here: https://github.com/markvanderloo/tinytest/blob/bcfec2d/pkg/R/tinytest.R#L698

This issue was fixed 4yrs ago for run_test_dir b6d4589 , but remains for run_test_file.