Drop paste v1 support

Starting from version [v2.0.0](https://github.com/PrivateBin/PrivateBin/releases/tag/2.0.0), the paste v1 support [has been completely removed](https://github.com/PrivateBin/PrivateBin/pull/1591) from PrivateBin. 
Therefore, I propose to remove paste v1 support from PBinCLI to clean up the project from legacy code.
If you agree with this idea, I can work on this issue