[Analytics Hub] Update colors to match designs for 0% change

[rachelmcr]

Currently we're using a red color for the delta tag and line chart when an analytics stat has 0% change. However, I noticed the designs have a gray color specified for 0% change:

• Delta tag background: #F6F7F7 (Color Studio gray, shade 0)
• Line chart line: #8A8A8E (Closest equivalent is Color Studio gray, shade 30)

Current	Designs

[peril-woocommerce]

	Fails
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[peril-woocommerce]

	Fails
🚫	Please add a feature label to this issue. e.g. 'feature: stats'

Generated by 🚫 dangerJS

[peril-woocommerce]

	Fails
🚫	Please add a feature label to this issue. e.g. 'feature: stats'

Generated by 🚫 dangerJS