[GRASS-git] [OSGeo/grass-addons] e15af6: Update name of core branch from master to main (#598)

[Vaclav Petras]

  Branch: refs/heads/grass7
  Home:   https://github.com/OSGeo/grass-addons
  Commit: e15af67a08f2024ac8f19bef3667f10339aaf2c4
      https://github.com/OSGeo/grass-addons/commit/e15af67a08f2024ac8f19bef3667f10339aaf2c4
  Author: Vaclav Petras <wenzeslaus at gmail.com>
  Date:   2021-08-22 (Sun, 22 Aug 2021)

  Changed paths:
    M .github/workflows/ci.yml
    M tools/cronjobs_osgeo_lxd/README.md
    M tools/cronjobs_osgeo_lxd/cron_grass74_releasebranch_74_build_bins.sh
    M tools/cronjobs_osgeo_lxd/cron_grass74_src_relbr74_snapshot.sh
    M tools/cronjobs_osgeo_lxd/cron_grass76_releasebranch_76_build_bins.sh
    M tools/cronjobs_osgeo_lxd/cron_grass76_src_relbr76_snapshot.sh
    M tools/cronjobs_osgeo_lxd/cron_grass78_releasebranch_78_build_bins.sh
    M tools/cronjobs_osgeo_lxd/cron_grass78_src_relbr78_snapshot.sh
    M tools/cronjobs_osgeo_lxd/cron_grass8_HEAD_build_bins.sh
    M tools/cronjobs_osgeo_lxd/cron_grass8_HEAD_src_snapshot.sh

  Log Message:
  -----------
  Update name of core branch from master to main (#598)

The development/default branch in the core repo was renamed from master to main.
This includes updates of the CI, comments and documentation.
It removes the mention of the master/main branch when the reference is not necessary.

Notably, this does not update the code for OSGeo cron jobs because name of branch is used there additionally as a directory name and it is part of a non-scripted part of the setup.
(This needs will be changed together with the setup on the OSGeo server.)