Normalize Whitespace: Removed unnecessary checks

[RunDevelopment]

This resolves #3016.

The typeof document === 'undefined' was unnecessary. The plugin does interact with the DOM but only in the before-sanity-check hook which is run inside highlightElement which is given a DOM element. So the plugin only tries to interact with the DOM if it is given a DOM element. Therefore, the check is unnecessary.

I also removed a duplicate typeof Prism === 'undefined' check. No idea why that was there.

[github-actions]

JS File Size Changes (gzipped)

A total of 1 files have changed, with a combined diff of -16 B (-1.5%).

file	master	pull	size diff	% diff
plugins/normalize-whitespace/prism-normalize-whitespace.min.js	1.1 KB	1.08 KB	-16 B	-1.5%

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