Delete the deprecated identifier macro

[joellabes]

Describe the feature

For a long time, identifer() has been labeled as deprecated:

dbt-utils/macros/cross_db_utils/deprecated/identifier.sql

Lines 2 to 6 in a976cdf

	{%- set error_message = '
	Warning: the `identifier` macro is no longer supported and will be deprecated in a future release of dbt-utils. \
	Use `adapter.quote` instead. The {}.{} model triggered this warning. \
	'.format(model.package_name, model.name) -%}
	{%- do exceptions.warn(error_message) -%}

Its time has come.

This one is pretty easy! Just a case of deleting the file. As far as I can see, it doesn't have any tests associated with it, and it's no longer used in any dbt_utils macros. If, when you do delete it, it causes some tests to fail, replace them with adapter.quote as needed.

Who will this benefit?

Appreciators of clean code everywhere

Are you interested in contributing this feature?

Nope - this one feels perfect for a community contribution!