tests: stop strdup'ing test input/output in sexpr parser test
tests: stop strdup'ing test input/output in sexpr parser test

We can just modify the passed in buffers without fear.

Signed-off-by: Josef 'Jeff' Sipek <a620f141433c70aa9e43778305a6c68cbfadfb25@josefsipek.net>

jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc