The tag is present in Lintian version 2.104.319. That is the most recent version we know about.
The given lines in the applicable override file refer to the same tag with the same context. It is redundant at best, and possibly indicates outdated overrides.
This condition is also flagged for renamed tags, for which it occurs perhaps more often as the overrides are adjusted for new tag names.
Please remove or adjust one of the overrides, whichever suits your purpose.
This tag cannot be masked or overridden.