Fix Readme.md prerequisites

[SinnoTogo]

Under the prerequisites of the Readme.md document we have the next line: pip3 install toml-cli

It shall be changed to: sudo pip3 install toml-cli

since the build script is run as sudo.

Also had to run the next command to add the keyrings for ti-debpks: curl -fsSL https://texasinstruments.github.io/ti-debpkgs/KEY.gpg | sudo gpg --dearmor -o /usr/share/keyrings/ti-debpkgs.gpg

Last but not least also had to run: sudo pip3 install jsonschema

[sskartheekadivi]

• Prerequisites have been updated
• ti-debpkgs keyring is no longer needed to be added on host.