Vagrant triggers plugin warning

[prondubuisi]

Running vagrant up with the vagrant triggers installed leaves a warning

WARNING: Vagrant has detected the `vagrant-triggers` plugin. This plugin conflicts
with the internal triggers implementation. Please uninstall the `vagrant-triggers`
plugin and run the command again if you wish to use the core trigger feature. To
uninstall the plugin, run the command shown below:

  vagrant plugin uninstall vagrant-triggers

Note that the community plugin `vagrant-triggers` and the core trigger feature
in Vagrant do not have compatible syntax.

To disable this warning, set the environment variable `VAGRANT_USE_VAGRANT_TRIGGERS`.

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