This updates the list of features in 'generic' and 'bleeding-edge' CPUs
in the backend to match
https://github.com/llvm/llvm-project/blob/4e0a0eae58f7a6998866719f7eb970096a2a52e9/clang/lib/Basic/Targets/WebAssembly.cpp#L150-L175.

It is hard to add a backend test for this, given that we don't have a
convenient way of testing the list of features included in each cpu like
the preprocessor test in Clang:
https://github.com/llvm/llvm-project/blob/4e0a0eae58f7a6998866719f7eb970096a2a52e9/clang/test/Preprocessor/wasm-target-features.c#L158-L208
And the current features for 'generic' and 'bleeding-edge' don't have a
separate backend test anyway.