This class was introduced in commit
fa3365430c5fb57d7c0b5f2bce9fbbe290be93c3 ("net: Use mockable time for
ping/pong, add tests"), but actually never used.
The previous diff touched most files in ./test/, so bump the headers to
avoid having to touch them again for a bump later.
-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./test/
-END VERIFY SCRIPT-