JIT

Remove PYTHON* env vars to isolate colour tests #198

Job	Run time
Interpreter (Debug)	7m 51s
Free-Threaded (Debug) (19)	12m 16s
i686-pc-windows-msvc/msvc (Debug)	18m 4s
i686-pc-windows-msvc/msvc (Release)	10m 9s
x86_64-pc-windows-msvc/msvc (Debug)	17m 47s
x86_64-pc-windows-msvc/msvc (Release)	11m 3s
aarch64-pc-windows-msvc/msvc (Debug)	5m 15s
aarch64-pc-windows-msvc/msvc (Release)	6m 58s
x86_64-apple-darwin/clang (Debug)	13m 30s
x86_64-apple-darwin/clang (Release)	10m 3s
aarch64-apple-darwin/clang (Debug)	8m 41s
aarch64-apple-darwin/clang (Release)	8m 42s
x86_64-unknown-linux-gnu/gcc (Debug)	8m 38s
x86_64-unknown-linux-gnu/gcc (Release)	5m 39s
aarch64-unknown-linux-gnu/gcc (Debug)	6m 14s
aarch64-unknown-linux-gnu/gcc (Release)	5m 0s
	2h 35m 50s

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