chore(mypy): enable `truthy-bool` error code #4254

Job	Run time
pyright	1m 45s
mypy	2m 19s
slotscheck	1m 27s
Test server integration (uvicorn<0.27.0)	1m 32s
Test Minimal Application with Base Dependencies	1m 19s
Test server integration (uvicorn>=0.27.0)	1m 27s
Test Minimal Pydantic 1 application	1m 24s
test-platform-compat	0s
validate	12s
test (3.10) / test	2m 49s
test (3.11) / test	2m 32s
test (3.12) / test	4m 11s
test (3.8) / test	3m 54s
test (3.9) / test	7m 5s
build-docs	3m 23s
upload-test-coverage	17s
codeql	2m 15s
sonar	1m 10s
	39m 1s

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