Fix typo in Mint.WebSocket.new() function doc

[mruoss]

Scheme is passed to upgrade/5, not new/5.

[coveralls]

Pull Request Test Coverage Report for Build 970178439a38cf5011711ff5d69ff6797907cb6f-PR-28

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 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 89.174%

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Totals
Change from base Build e76205eefd9227aa9d10a1a808025024f5144a6c:	0.0%
Covered Lines:	313
Relevant Lines:	351

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💛 - Coveralls

[the-mikedavis]

Thank you!