Remove deprecated text-* utils and utilities.scss

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What does this MR do and why?

This MR removes deprecated text-* classes and references to them aiming to finally get rid of the utilities.scss. It also removes references to said file.

Instances of text-1 can be safely replaced with gl-text-sm. For standard users this is the same font-size. I decided to replace of text-4 with gl-heading-2 because it is the closest match and seems visually unnoticable.

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