Use documented username/password for docker/login-action

[mwtoews]

Looking at #4584 there appears to be an unrelated issue with docker/login-action, showing the following:

Run docker/login-action@v3
  with:
    registry: ghcr.io
    username: OSGeo
    logout: true
  env:
    PUSH_PACKAGES: true
    CONTAINER: proj
Error: Password required

This PR updates the usage to follow the docs for the action for both ghcr.io and default Docker Hub registries.

[mwtoews]

Note that this PR skips the two relevant checks:

these need to be triggered via ${{ env.PUSH_PACKAGES == 'true' }} set with logic:

PUSH_PACKAGES: ${{ github.repository_owner == 'OSGeo' && github.event_name != 'pull_request' && (matrix.container == 'proj' || (matrix.container == 'proj-docs' && github.ref_name == 'master')) }}