Remove usage of UIColor.Photon.Grey60

[lmarceau]

📄 Context

We have deprecated colors in our app under photon-colors.swift we shouldn't be using anymore. I am creating some tasks so we remove them one by one to ensure we make small PRs and evaluate colors usage per their context.

✏ Requirements

1. UIColor.Photon.Grey60 is used under LoginsHelper class. Turns out it's used in a class func replace(_ base: String, keys: [String], replacements: [String]) -> NSMutableAttributedString that isn't called anymore. So let's remove it from the code.
2. UIColor.Photon.Grey60 should be removed from the photon-colors.swift file.

ℹ️ Reference Person

@lmarceau

┆Issue is synchronized with this Jira Task