Bump version for 4.2.0 release #1305

Job	Run time
py312 on alpine	59s
Python 3.7 on win32	1m 47s
py312 on alpine:aarch64	1m 24s
pep8,packaging on linux, Rust stable	58s
Python 3.12 on win32	2m 41s
Python 3.7 on macos-13	1m 24s
py312 on ubuntu-rolling:aarch64	1m 14s
mypy on linux, Rust stable	37s
Python 3.7 on win64	2m 8s
Python 3.12 on macos-13	1m 14s
py37 on linux, Rust stable	37s
Python 3.12 on win64	2m 52s
Python 3.12 on macos-latest	35s
py38 on linux, Rust stable	36s
py39 on linux, Rust stable	31s
py310 on linux, Rust stable	35s
py311 on linux, Rust stable	37s
py312 on linux, Rust stable	34s
py313 on linux, Rust stable	44s
pypy3 on linux, Rust stable	56s
pypy3 on linux, Rust stable	1m 4s
py312 on linux, Rust 1.64.0	2m 27s
py312 on linux, Rust beta	40s
py312 on linux, Rust nightly	45s
all-green	2s
	28m 1s

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