docs: fix typo in z.object (#2570)

Author: m7yue

README.md

@@ -1204,7 +1204,7 @@ Starting from this object:
 
 ```ts
 const user = z.object({
-  email: z.string()
+  email: z.string(),
   username: z.string(),
 });
 // { email: string; username: string }
@@ -1269,7 +1269,7 @@ Starting from this object:
 
 ```ts
 const user = z.object({
-  email: z.string()
+  email: z.string(),
   username: z.string(),
 }).partial();
 // { email?: string | undefined; username?: string | undefined }