Don't redundently document directory configuration in plugins

Background

A left over item following the merge of !776 (merged)

This item describes Technical debt.

See !776 (comment 107972976) for the original comment.

Task description

Change all of the individual source plugins to no longer redundantly document the directory configuration; instead they should all have a mention that the reader should refer to the built-in functionality section of the Source docs for common configurations.

The same should go for the BuildElement implementations in plugins/elements/.

• Sources
• BuildElements

Acceptance Criteria

Source and build elements no longer redundantly document the directory configuration.

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