changed v2 to main

[phLeung]

Problem

My Yocto build kept breaking because my build could not fetch Docker Compose resources from the v2 branch. Upon further investigation, the docker compose v2 branch does not exist anymore. The v2 branch was most likely merged with main branch.

Solution

Edited docker-compose_git.bb to point to the main branch of the docker compose repo. This fixed my yocto build.

I would like this PR to be reviewed and accepted if possible.