[LV] Move new epilog-vectorization-widen-inductions.ll to AArch64 dir.

The test requires the AArch64 backend, so move it to the right subdir.

diff --git a/llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-widen-inductions.ll b/llvm/test/Transforms/LoopVectorize/AArch64/epilog-vectorization-widen-inductions.ll
similarity index 100%
rename from llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-widen-inductions.ll
rename to llvm/test/Transforms/LoopVectorize/AArch64/epilog-vectorization-widen-inductions.ll