gh-129707: Check Tools/build/compute-changes.py with mypy (#129708)

Co-authored-by: Adam Turner <[email protected]>
Co-authored-by: Hugo van Kemenade <[email protected]>

Author: 3 people

Tools/build/mypy.ini

@@ -1,5 +1,7 @@
 [mypy]
-files = Tools/build/generate_sbom.py
+files =
+    Tools/build/compute-changes.py,
+    Tools/build/generate_sbom.py
 pretty = True
 
 # Make sure Python can still be built