skip adding commas in extends list closes Issue9563

[homberghp]

solves #9563

Added a test to ensure the non-generic extends clause keeps working

The change is in CasualDiff#diffList2

To improve readability, indented a small part in CasualDiff#diffClassDef

The bug caused the addition of superfluous commas in a list of generic types in a extends list of an interface.

I did not use any LLM or AI in this solution.

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