Migrate gl-text-green-500 -> gl-text-success

What does this MR do and why?

Migrates all gl-text-green-500 that are styling icons to gl-text-success, ideally, we should migrate these to gl-fill-icon-color but the way GlIcon works is when there is no variant, the fill is set to currentColor which gets the value from the inherited text color attribute. gl-fill-icon-color would be appropriate if applied to the element itself but in some cases, such as !174424 (comment 2250962929), the styling is applied to the parent.

When we go through our stylings page by page, we can update these classes because we will be validating the entire page, but as this MR has no validation, it is important that we replace like for like.

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Related to #503118 (closed)