Revert "fix pre-push to compare with main on first push"

[shtukas]

Reverts #2605 , because it breaks pushing for me.

support-service-lambdas % git push origin HEAD                 
fatal: bad revision 'origin/ph-20241219-1154-upgrade'
husky - pre-push script failed (code 128)
error: failed to push some refs to 'https://github.com/guardian/support-service-lambdas.git'

[johnduffell]

sorry about that, it's strange, I thought I tested all four combinations carefully! Thanks for reverting it. I also didn't realise that a nonzero exit code would kill the whole script without the -e flag.
According to git docs hooks are just "programs" and there's no #! line at the top of the file, so I wonder if the default shell could affect things

@shtukas Is your default shell set up to die on error by default? Perhaps this script needs to be more explicit.