Remove the postinstall script which didn't work

[robin-crazygames]

Removed the postinstall step, because it doesn't work and does nothing in practice. E.g. running npm i results in

> ./npm-postinstall.sh

cp: failed to get attributes of './include-media/tests/index.scss'$'\n''.': No such file or directory
cp: failed to get attributes of './bourbon/bundle/ruby/3.1.0/gems/cucumber-2.99.0/lib/cucumber/formatter/cucumber.css'$'\n''.': No such file or directory

So the 2 cp command in the postinstall step don't do anything. And since those two do nothing, the last find command doesn't find any matches and also does nothing.

In short, the whole postinstall step can be removed.

🏷 Type of documentation

• new bid adapter
• update bid adapter
• new feature
• text edit only (wording, typos)
• bugfix (code examples)
• new examples

📋 Checklist

• Related pull requests in prebid.js or server are linked -> Paste link in this list or reference it on the PR itself
• For new adapters check submitting your adapter docs

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