selftests: remove reference to prime_numbers.sh

selftests: remove reference to prime_numbers.sh

Remove a leftover shell script reference from commit 313b38a6ecb4
("lib/prime_numbers: convert self-test to KUnit").

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202502171110.708d965a-lkp@intel.com
Fixes: 313b38a6ecb4 ("lib/prime_numbers: convert self-test to KUnit")
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250217-fix-prime-numbers-v1-1-eb0ca7235e60@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>