ci: disable incremental tests

Too much flakiness across the board: https://codeberg.org/ziglang/zig/issues?q=&type=all&sort=relevance&labels=747060&state=open&milestone=0&project=0&assignee=0&poster=0
953ca759c2Alex Rønne Petersen committed on 1/21/2026, 4:21:05 PMparent7337946
20 files changedLine totals unavailable