fix: move the required validation to the if schema

This commit moves the `required` validation for the example schema in
ch05's lesson "Expanding If-then-else" and places it in the `if`
subschema, so that it applies only for the purpose of the condition.

Author: eitamal

content/05-Conditional-Validation/06-Expanding-If-then-else/instructions.mdx

@@ -41,13 +41,13 @@ Using the `not` keyword with the `if-else` keyword can look something like this:
   "if": { 
     "properties": {
        "status": { "const": "employed" } 
-    } 
+    }, 
+    "required": ["status"]
   },
   "then": { 
     "not": { "required": ["unemploymentBenefits"] 
     } 
-  },
-  "required": ["status"]
+  }
 }
 ```
 - If `status` is `"employed"`, the `unemploymentBenefits` field **must not** be present.