Update: Remove Blaze widget header for the mobile app

[enejb]

Related to pe7hp4-aM-p2

Proposed Changes

• Remove the Blaze Branding header from the widget for when the widget is displayed in the mobile app.

Testing Instructions

• Load this PR.
• Using the Mozilla/5.0 (iPhone; CPU iPhone OS 14_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.3 Mobile/15E148 wp-android UA header. You can change it in the developer tools preview

Notice that the header is not there any more.

Notice that the header is there when using a regular iPhone or Android browser headers.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-56960

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-56960&env=jetpack

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[zwarm]

Nice work @enejb . I tested by launching a webview within the Jetpack app. As expected; the header does not show.