docs: Fix simple typo, submenut -> submenu

[timgates42]

There is a small typo in docs/scripts/collapse.js.

Should read submenu rather than submenut.

[coveralls]

Pull Request Test Coverage Report for Build 962

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 90.52%

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Totals
Change from base Build 948:	0.0%
Covered Lines:	576
Relevant Lines:	589

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💛 - Coveralls

[lancedikson]

Hi, @timgates42! I'm afraid, the scripts folder is fully autogenerated by the jsdoc tool, so if even I apply this change, it will still change back to the version with a typo once I run docs regeneration ¯_(ツ)_/¯

[lancedikson]

So, closing the PR as there's no way to influence those scripts like that :)