t4122: use test_write_lines from test-lib-functions
t4122: use test_write_lines from test-lib-functions

Instead of using a custom lecho function, just use what the test
framework already gives us.

Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git