fix: incorrect int to float strict comparison in gutenberg_tinycolor_bound01()

[justlevine]

What?

This PR fixes an issue in gutenberg_tinycolor_bound01() where an int is strict-compared to a float, resulting in an always-false comparison.

Why?

While this issue was surfaced by PHPStan (via #66693) it can be remediated independently as part of #66598

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

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