Revert "feat: pass private key as env variable SSH_KEY"

This reverts commit 73f25ab8d24962dab50447ac0a50bb6849becac7.

ssh_router.sh

@@ -125,7 +125,6 @@ start_container_if_needed() {
       --user "$DEV_USER" \
       --hostname "$WORKSPACE" \
       --label auto-cleanup=true \
-      -e SSH_KEY="$(cat $HOME/secrets/$WORKSPACE/id_ed25519)" \
       -v "/mnt/private/workspaces-data/public/$WORKSPACE:/app/public" \
       -v "/mnt/private/workspaces-data/private/$WORKSPACE:/app/private" \
       -v "$HOME/secrets/$WORKSPACE/gitconfig:/home/$DEV_USER/.gitconfig:ro,Z" \