revert: fix typing errors after dependencies update

Signed-off-by: Sami Mazouz <sychocouldy@gmail.com>

framework/core/js/src/common/Application.tsx

@@ -433,6 +433,8 @@ export default class Application {
     // a dud response, we don't want the application to crash. We'll show an
     // error message to the user instead.
 
+    // @ts-expect-error Typescript doesn't know we return promisified `ReturnType` OR `string`,
+    // so it errors due to Mithril's typings
     const defaultDeserialize = (response: string) => response as ResponseType;
 
     // When extracting the data from the response, we can check the server