"Configurable Build Attributes" documentation is duplicated

### Page link:

https://bazel.build/configure/attributes

### Problem description (include actual vs expected text, if applicable):

The documentation for Configurable Build Attributes is duplicated. Doc sources are located in both `site/en/configure/attributes.md` and `site/en/docs/configurable-attributes.md`.

As a consequence, @vorburger 96e29dc fix some line break in `site/en/docs/configurable-attributes.md` but those modifications do not reach [bazel website here](https://bazel.build/configure/attributes) because the source of truth for that page is actually `site/en/configure/attributes.md`.

### Where do you see this issue? (include link to specific section of the page, if applicable)

The discrepancy is located at this line:
> Matches must be unambiguous: if multiple conditions match then either

### Any other information you'd like to share?

_No response_

Read site/en/configure/attributes.md and site/en/docs/configurable-attributes.md, then compare the duplicated Configurable Build Attributes content around the line about unambiguous matches. Determine which source generates the linked page, consolidate the documentation so there is one authoritative version, and verify the discrepancy is gone.

Written by the indexing model from the issue text.