[wasm] Remove wrong SWIFT_HOST_VARIANT_ cmake caches

`NONE` is completely wrong and testing macro feature requires a valid
value of those cmake variables now for `config.host_triple`

Author: kateinoigakukun

cmake/caches/Runtime-WASI-wasm32.cmake

@@ -1,7 +1,5 @@
 set(SWIFT_PRIMARY_VARIANT_SDK WASI CACHE STRING "")
 set(SWIFT_PRIMARY_VARIANT_ARCH wasm32 CACHE STRING "")
-set(SWIFT_HOST_VARIANT_SDK NONE CACHE STRING "")
-set(SWIFT_HOST_VARIANT_ARCH NONE CACHE STRING "")
 
 set(SWIFT_SDKS WASI CACHE STRING "")