Remove auto-update feature from agent

[remagpie]

CodeChain agent tries to find & update the .git folder in the CodeChain directory, and build a new binary.
However, most of the machines running CodeChain don't have enough performance to build a binary, so it's useless now.
We might need some kind of auto-updating feature for CodeChain agent in the future, but it will be different from the current implementation.