Editorial: combine the two subclauses for HasCallInTailPosition

[bakkot]

HasCallInTailPosition was defined in one place even prior to the more general SDO consolidation.

But that one place was split up into two subclauses. Prior to SDO consolidation that wasn't remarkable, but afterwards it was, since no other SDO split its parts into subclauses like this. Plus it makes static analysis harder. So remove the subclauses.

I recommend reviewing this PR with whitespace changes suppressed.