Fix tooltip hyperlink color in dark mode

[emyller]

How are you running Flagsmith

• [ ] Self Hosted with Docker
• [ ] Self Hosted with Kubernetes
• [ ] SaaS at flagsmith.com
• [ ] Some other way (add details in description below)

Describe the bug

When in dark mode, the hyperlink text in tooltips is barely visible.

Steps To Reproduce

Many user workflows in the UI can lead to this. For example:

• In the Features page, update any feature flag.
• Create or edit any change request.

Expected behavior

All text should be readable.

Screenshots