Use project prefixes for dependencies in group_notify.info.yml

Problem/Motivation

Trying to install this module via composer fails:

drupal/group_notify 1.3.0 requires drupal/gnode *

I think that's because group_notify.info.yml has:

dependencies:
  - gnode

Proposed resolution

Use:

dependencies:
  - group:gnode

as intended (see #2798891: Define project dependencies in core module .info files)

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet