Improve back button style for Add cluster page

<img width="919" alt="Screenshot 2023-06-20 at 12 32 35 AM" src="https://github.com/redhat-developer/vscode-openshift-tools/assets/3133356/9cb9a149-1897-47ea-9588-dfa6a2b7453f">


We need to improve the UX of the back button and make it more intuitive.