[SVE] Remove calls to VectorType::getNumElements from AsmParserTest

Reviewers: efriedma, c-rhodes, david-arm, kmclaughlin, fpetrogalli, sdesmalen

Reviewed By: efriedma

Subscribers: tschuett, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83339