core/cmd_print: remove unused oldshell code

[XVilka]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

pm and pg commands were converted to rzshell long time ago, remove old and unused implementation: #1590

Test plan

CI is green

[wargio]

didn't we finish with the p commands?

[XVilka]

@wargio not yet, five more remain: #1590
I will do two or three more commands later today.