runtime: remove minSched hack for wasm

I am not entirely sure what it's doing (it seems related to js.FuncOf),
but tests still seem to pass when this code is removed. So let's remove
it.

src/runtime/runtime_wasm_js.go

@@ -4,13 +4,6 @@ package runtime
 
 type timeUnit float64 // time in milliseconds, just like Date.now() in JavaScript
 
-// wasmNested is used to detect scheduler nesting (WASM calls into JS calls back into WASM).
-// When this happens, we need to use a reduced version of the scheduler.
-//
-// TODO: this variable can probably be removed once //go:wasmexport is the only
-// allowed way to export a wasm function (currently, //export also works).
-var wasmNested bool
-
 var handleEvent func()
 
 //go:linkname setEventHandler syscall/js.setEventHandler