fix: added decoy col to confidence reports

[jspaezp]

Purpose

Re-adds the decoy column in the reports

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Has linting/formatting been run? (make lint, make format, make check)
• Was it tested locally? (make test)
• Has the changelog been updated?
• Have the docs been updated? (I might need help with this one ... we need a smart way to get percolator available)
• The level of testing this PR includes is appropriate.
• No features have been dropped (or note which ones and why).

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