selftests: fib_rule_tests: Remove unused functions

The functions are unused since commit 816cda9a ("selftests: net:
fib_rule_tests: add support to select a test to run"). Remove them.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20240814111005.955359-2-idosch@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>