[TIDY FIRST] Fix typing issues in dbt/core/tasks/clean.py

[QMalcolm]

Resolves #10616

Problem

There were type issues in dbt/core/tasks/clean.py

Solution

Fix the typing issues in dbt/core/tasks/clean.py

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.10%. Comparing base (f25a474) to head (a1e4086).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10617      +/-   ##
==========================================
- Coverage   88.91%   86.10%   -2.81%     
==========================================
  Files         180      180              
  Lines       22760    22760              
==========================================
- Hits        20237    19598     -639     
- Misses       2523     3162     +639     

Flag	Coverage Δ
integration	86.10% <100.00%> (-0.12%)	⬇️
unit	?

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Components	Coverage Δ
Unit Tests	86.10% <100.00%> (-2.81%)	⬇️
Integration Tests	86.10% <100.00%> (-0.12%)	⬇️