Add Python package classifier for Python 3.12 support. #1307

Job	Run time
Run JS linters	2m 9s
Check lint and rustfmt	49s
Check rustdoc WASM target	10s
Check fuzz targets	24s
Run tests	2m 27s
Python tests and maturin build (3.9)	56s
WASM tests	1m 2s
pre-publish checks	0s
Python tests and maturin build (3.10)	1m 25s
Python tests and maturin build (3.11)	57s
Python tests and maturin build (3.12)	1m 36s
All CI stages	2s
pre-publish checks	0s
publish trustfall_filetests_macros	0s
publish trustfall_core	0s
publish python trustfall	0s
publish trustfall_derive	0s
publish trustfall	0s
publish trustfall_stubgen	0s
	11m 57s

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