Don't require integrations-schema for linting only

If the golang version of the integrations repo is checked out within GOPATH and thus integrations-schema is not present in the parent directory, linting step fails:
```
❯ ./build.sh lint
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 13418 100 13418 0 0 78795 0 --:--:-- --:--:-- --:--:-- 84924
'../integrations-schema/docker-compose.yml' is missing to start schema
```

The ask of this issue is to decouple linting from other dependencies (will file a separate issue for the relative path requirement)

Start with build.sh and run ./build.sh lint in a checkout where integrations-schema is absent from the parent directory. Trace why the linting step requires ../integrations-schema/docker-compose.yml. Done means linting runs without that dependency, while the separate relative-path requirement remains out of scope.

Written by the indexing model from the issue text.