meta: bump version to v0.20.6 #3

Job	Run time
pypi / Build source dist	6s
crates / Publish Rust package	32s
npm / Build Wasm binaries	2m 2s
npm / Build NodeJS binaries on ubuntu-20.04	1m 27s
npm / Build NodeJS binaries on windows-latest	4m 4s
npm / Build NodeJS binaries on macos-latest	1m 55s
pypi / Build wheels on windows-latest (AMD64)	1m 23s
pypi / Build wheels on ubuntu-latest (x86_64)	1m 22s
pypi / Build wheels on ubuntu-latest (aarch64)	3m 20s
pypi / Build wheels on macos-latest (arm64)	1m 39s
pypi / Build wheels on macos-latest (x86_64)	1m 54s
pypi / Publish Python package	54s
npm / Publish NodeJS package	16s
	20m 54s

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