[LV][NFC] Remove more unused function attributes from tests (#190786)
Following on from PR #188185 I've removed some more function attributes
from tests that weren't adding any value. As part of this patch I've
also removed some unnecessary `Function Attrs:` comments that live above
functions.
I suspect that there are other attributes that can be removed, for
example see ARM/arm-ieee-vectorize.ll. However, I haven't had chance to
look into these yet as they are more FP and/or target specific and
perhaps require more thought.