Remove support for scoped static methods

This is intended to address #834 where we don't actually want methods scoped
like this! Instead we'll provide one unique accessor for the `window` object
itself.

crates/backend/src/codegen.rs

@@ -779,9 +779,6 @@ impl TryToTokens for ast::ImportFunction {
                 }
                 class_ty = Some(ty);
             }
-            ast::ImportFunctionKind::ScopedMethod { ref ty, .. } => {
-                class_ty = Some(ty);
-            }
             ast::ImportFunctionKind::Normal => {}
         }
         let vis = &self.function.rust_vis;