[SCEV] Don't use std::make_pair; NFC

`{A, B}` reads cleaner than `std::make_pair(A, B)`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261392 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed