`test_elif_deep` fails on s390x with `RecursionError`

test_elif_deep generates 999 nested elif branches, which exceeds CPython's Py_C_RECURSION_LIMIT of 800 on s390x (set lower due to the z/Architecture ABI's 160-byte-per-frame register save area). The flat elif codegen from #759 is unconditional, so the test depth can be lowered without reducing coverage.

Environment:

• Python version: 3.13
• Jinja version: latest (3.1.6)