chore: remove prepack and postpack npm scripts

[ehmicky]

See #4041 (comment)

prepack and postpack do not seem to be used anymore. I believe those might have been remnants from OCLIF.

npm publish already prunes devDependencies before bundling, so those scripts seem to be noop. I tried to run npm pack --dry and it seemed to create the same bundle with or without those scripts.

Those npm scripts are a problem because prepack is run before prepare. prepare runs husky, which is a devDependency. However husky is then missing due to prepack pruning it. This prevents us from running npm publish, and making new releases of Netlify CLI.

After merging this, we should be careful when releasing and do some manual testing to ensure this does not break anything.

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[github-actions]

📊 Benchmark results

Comparing with 8351e25

Package size: 448 MB

⬇️ 0.00% decrease vs. 8351e25

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└───┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴──>
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Legend

• T-9 (8351e25): 448 MB
• T-8 (41e6729): 448 MB
• T-7 (5e6df42): 448 MB
• T-6 (70df1b8): 448 MB
• T-5 (064049b): 448 MB
• T-4 (baafd99): 448 MB
• T-3 (bea66fe): 448 MB
• T-2 (e281a90): 448 MB
• T-1 (90449e5): 448 MB
• T (current commit): 448 MB