Remove OICP 2.1 https link & public message

[DVS01Berlin]

Please review the removal of the OICP 2.1 https link, as well as public message about the shutdown of OICP 2.1.

[DVS01Berlin]

Hi Mohammad & Hamed,

Please review the changes to the README file which includes:

• updating number of partner countries from 43 to 52
• removal of OICP 2.1 https link
• public message confirming OICP 2.1 shutdown on 13. April 2023.

Thank you, Dave