Update Model Family dropdown to reflect "Claude" for Claude in GitLab Duo Admin

Now that Claude 4 is supported via Bedrock and self-managed GitLab, we should ensure the Model Family dropdown in the GitLab Duo Admin UI reflects this update.

According to @sbitters, the dropdown was updated to show just "Claude" for the Claude 4 model.

If not, we should:

• Update the dropdown label to "Claude" instead of "Claude 3".
• Ensure consistency across relevant model selection UIs.

Related discussion: https://gitlab.slack.com/archives/C05GK6M7FBQ/p1756101399723949