bpf/tests: Remove duplicate JSGT tests

It seems unnecessary that JSGT is tested twice (one before JSGE and one
after JSGE) since others are tested only once. Remove the duplicate JSGT
tests.

Fixes: 0bbaa02b ("bpf/tests: Add tests to check source register zero-extension")
Signed-off-by: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Link: https://lore.kernel.org/bpf/20231130034018.2144963-1-yujie.liu@intel.com