docs(upgrade): fix import (#2997)

Co-authored-by: James Daniels <jamesdaniels@google.com>

Author: Albejr

docs/version-7-upgrade.md

@@ -103,7 +103,7 @@ In AngularFire v7 working with multiple instances was difficult, in the new SDK
 
 ```ts
 import { FirebaseApp, FirebaseApps } from '@angular/fire/app';
-import { Storage, StorageIsntances } from '@angular/fire/storage';
+import { Storage, StorageInstances } from '@angular/fire/storage';
 
 export class Foo {
     constructor(