Enable checking for f strings #13128

Job	Run time
Test suite with Python nightly	2m 19s
Test suite with py38-ubuntu, mypyc-compiled	2m 17s
Test mypyc suite with 32-bit Python	2m 6s
Test suite with py38-windows-64	2m 3s
Test suite with py39-ubuntu	2m 18s
Test suite with py310-ubuntu	2m 19s
Test suite with py311-ubuntu, mypyc-compiled	2m 18s
Test suite with py312-ubuntu, mypyc-compiled	2m 18s
mypyc runtime tests with py39-macos	2m 19s
mypyc runtime tests with py38-debug-build-ubuntu	2m 18s
Type check our own code (py38-ubuntu)	1m 50s
Type check our own code (py38-windows-64)	2m 4s
Formatting and code style with Black + ruff	34s
	27m 3s

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