Resolve MappedFileLineReaderTest on Windows and macOs builds

[bric3]

On Windows the build fails with

• MappedFileLineReaderTest.find_start_position_given_last_lines()

  org.opentest4j.AssertionFailedError:
  expected: 42L
  but was : 43L

• MappedFileLineReaderTest.can_read_from_position()

  org.opentest4j.AssertionFailedError:
  expected: 183L
  but was : 186L

• MappedFileLineReaderTest.should_watch_with_channel_sink(Path)

java.io.IOException: Failed to delete temp directory C:\Users\RUNNER~1\AppData\Local\Temp\junit8439001560896197356. The following paths could not be deleted (see suppressed exceptions for details): , test4653189040998961269log

On MacOS the build fails with

• MappedFileLineReaderTest.should_watch_with_channel_sink(Path)

org.opentest4j.AssertionFailedError:
expected: 592L
but was : 38L