Draft: User activity redesign

This MR is a part of the ✨ Beautifying our UI (15.5) ✨ 

What does this MR do and why?

This MR updates the user activity list UI. It is a part of the user profile redesign effort &7902. The related design is here.

Changes within the current MR:

• Remove the user avatar and name
• Change the icon color to #666666
• Change the text color to #303030
• Change the event type font to bold
• Add underline to all links

The activity events partial is used in 3 places:

1. User's profile -> overview tab -> activity section
2. User's profile -> activity tab
3. /dashboard/activity page

The MR updates only user profile activity events (1 and 2)

Screenshots or screen recordings

User profile -> overview tab

Before	After

User profile -> activity tab

Before	After

Dashboard activity page (no visual changes)

Before	After

How to set up and validate locally

1. Go to the user profile
2. Select the overview tab
3. Select the activity tab

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Review progress:

• UX review
• backend developer review
• backend maintainer review
• frontend developer review
• frontend maintainer review

Related to #374580 (closed)