[llvm] [TTI] Remove hasActiveVectorLength hook. NFC (PR #152977)

[Luke Lau via llvm-commits]

lukel97 wrote:

> This is required for other analysis, like early loop access analysis to check for support of some non-power-of-2 properties, like store-load dep distance

Oh for https://github.com/llvm/llvm-project/pull/137873? I see, maybe there's a better name for this hook for this though. I feel like it's not strictly related to VP intrinsics?

https://github.com/llvm/llvm-project/pull/152977