Closes #898 Update close icon on upsell banners and admin bar

[remyperona]

Description

Fixes #898

Update close icon to use default icon from WP

Type of change

• [x] Enhancement (non-breaking change which improves an existing functionality).

Detailed scenario

• With quota < 20%
• Display upsell banner on settings or bulk optimization page
• Display admin bar Imagify sub-menu
• Close icon is updated to default icon used in WP and in white

Technical description

Documentation

Updated class used + CSS color

Mandatory Checklist

Code validation

• [x] I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• [x] I triggered all changed lines of code at least once without new errors/warnings/notices.

Code style

• [x] I wrote a self-explanatory code about what it does.
• [x] I did not introduce unnecessary complexity.

[Mai-Saad]

@Tabrisrp Thanks for the PR. 1- settings page :heavy_check_mark: 2- Bulk page => not sure why icon is grey + the one in the page banner has underline 3- admin bar from WP dashboard page 4- the notice when click bulk optimization link while having no credit (not mentioned in main ticket but just here for reference)

@Tabrisrp Any idea why 2,3 has the icon grey and may be underlined?

[remyperona]

I pushed an update for the CSS for cases 2 and 3.

[Mai-Saad]

Thanks, @Tabrisrp Looks good now.