scripts/spdxcheck-test.sh: Drop python2

Since commit d0259c42 ("spdxcheck.py: Use Python 3"), spdxcheck.py
explicitly expects to run as python3 script, there is no further point
in attempting to test with python2.

Cc: Bert Vermeulen <bert@biot.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210707210600.7266-1-nm@ti.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>