update the instance/source optional implementation note to reflect web reality

Author: Guy Bedford

document/js-api/index.bs

@@ -1332,7 +1332,7 @@ This document defines a host environment for WebAssembly. It enables a WebAssemb
 
 WebAssembly modules can be used in a module graph with ECMAScript modules and Source Phase Imports.
 
-Note: It is possible to implement the Wasm-ESM integration in two stages. In the first stage only source phase imports of Wasm are supported (`import source fibModule from "./fib.wasm"`). In the second stage, evaluation phase imports would be supported too (`import { fib } from "./fib.wasm"`). If initially implementing just source phase imports, the `GetExportedNames`, `ResolveExport`, `InitializeEnvironment`, and `ExecuteModule` abstract operations can be implemented as abstract operations unconditionally throwing a `SyntaxError` exception. In this case, module fetch and CSP integration is still required to be implemented as specified in this proposal. Implementers are encouraged to ship both stages at once, but it is deemed OK for implementers to initially ship the first stage and then quickly follow up with the second stage, if this aids "time to ship" in implementations.
+Note: While this specification defines both a Source Phase Imports integration and an evaluation/instance phase integration, implementations may choose to implement only the Source Phase Imports as own smaller proposal without implementing the full evaluation/instance phase import form. In this case, the `ResolveExport` abstract operation should be implemented as returning null, and the `InitializeEnvironment` and `ExecuteModule` abstract operations implemented as unconditionally throwing a `ReferenceError` exception.
 
 <dfn export>WebAssembly Module Record</dfn>s are a subclass of [=Cyclic Module Record=] which contain WebAssembly code. WebAssembly Module Records have one additional internal slot:
     * \[[WebAssemblyModule]] : a WebAssembly {{Module}} object