Fix fork button being disabled for users who can fork to group

What does this MR do?

Enables the fork button for users who can fork into a group but not their own namespace.

The behaviour of this button was changed to be disabled for users who have exceeded their project limit. This caused an issue where the user could actually fork the project to a group namespace but not their own. This behaviour was actually already possible, users just had to navigate directly to forks/new to see the option.

Screenshots (if relevant)

If a user can fork to a group but not their own namespace they will see this & not be able to click the button.

If a user can't fork into a group or their own namespace they see this.

What are the relevant issue numbers?

Closes #38462 (closed)