glsl/tests/lower_jumps: fix generated sexpr's for loops

glsl/tests/lower_jumps: fix generated sexpr's for loops

In 088494aa (as well as other commits in the series) Paul Berry modified
the tests for lower_jumps to account for the fact that the s-expression
for the loop IR instruction changed from
(loop () () () () (statements...)) to (loop (statements...)), but he
forgot to update create_test_cases.py which he used to create the tests.
Fix that, so that now create_test_cases.py is synced with the generated
tests.

Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>