Updated Clone via HTTPS documentation

What does this MR do?

Many users face issues while cloning the project following this documentation. When they clone via HTTPS, it asks for Password where user should provide Personal Access Token and they mistakenly provide their GitLab account's password which shows error remote: HTTP Basic: Access denied. Moreover if they try again it shows the same error without even asking them to reenter the correct Password.

This MR updates Clone via HTTPS documentation and provides an option to clone while adding username in the clone URL, so that it asks for Password again.

Related issues

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