Drop prebuilds of Node.js v21 and Electron v25 #491

Job	Run time
Testing Node 18 on ubuntu-20.04	1m 30s
Testing Node 20 on ubuntu-20.04	55s
Testing Node 22 on ubuntu-20.04	56s
Testing Node 18 on macos-latest	1m 22s
Testing Node 20 on macos-latest	1m 5s
Testing Node 22 on macos-latest	54s
Testing Node 18 on macos-14	41s
Testing Node 20 on macos-14	34s
Testing Node 22 on macos-14	41s
Testing Node 18 on windows-2019	3m 32s
Testing Node 20 on windows-2019	3m 31s
Testing Node 22 on windows-2019	3m 28s
Publishing to NPM	0s
Prebuild on Linux (${{ matrix.arch }})	0s
Prebuild on alpine (${{ matrix.arch }})	0s
Prebuild on alpine	0s
Prebuild on ${{ matrix.os }}	0s
	19m 9s

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