remove git check, restore raspbian check

[ryanrhee]

• git is no longer needed in this script
• the raspbian check may have been erroneously removed?

[ryanrhee]

original check was restored from git history; see https://github.com/TheRemote/Ubuntu-Server-raspi4-unofficial/commit/75b1f7df7a1a7a0e55bf593eed135c0028b87d6c

[samip5]

That would be a bad idea to include as that would require you to execute it from Rasbian which is not always wanted or warrented.