ENH Don't include installer if it's not needed

[GuySartorelli]

Description

Whenever we add a new repository that isn't a module/recipe/theme, we have to update a constant in order to tell the matrix generator not to add installer for it.

Instead of doing that, the generator just shouldn't try to add installer for those. Anything that isn't a recipe, a module, or a theme but which needs installer for its tests to run should explicitly add installer as a dev dependency.

I'm making this change instead of adding the new standards repo to the const.

Issues

• Validate @method docblock tag in CI .github#171

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