docs vm.SourceTextModule: Instantiate() abstract operation has been replaced with InitializeEnvironment()

[Jamesernator]

The docs for vm.SourceTextModule.prototype.instantiate() contain a link to Instantiate() however this abstract method has been replaced with InitializeEnvironment() and so the link is now broken (it now points to Link()).

It might be worth renaming the .instantiate() method to .initializeEnvironment(), but regardless a doc update needs to be made to point to initialize environment.

[devsnek]

I will update this