selftests/bpf: Retire test_sock_addr.(c|sh)

Fully remove test_sock_addr.c and test_sock_addr.sh, as test coverage
has been fully moved to prog_tests/sock_addr.c.

Signed-off-by: Jordan Rife <jrife@google.com>
Link: https://lore.kernel.org/r/20240510190246.3247730-14-jrife@google.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>