deps: bump wasmtime (0.25.0 -> 0.26.0) (#3345)

* deps: bump wasmtime-go (0.25.0 -> 0.26.0)

I'm not entirely sure why some fluff of go.uber.org/automaxprocs was
removed, but I'm happy with the result. ;)

* wasm_sdk: use GetFunc(...) instead of GetExport(...).Func()

This added convenience function from wasmtime-go came in with the bump.

Signed-off-by: Stephan Renatus <stephan.renatus@gmail.com>