Fix tests: "infix modifier required" and "operator modifier required" errors

idea/testData/intentions/convertFunctionToProperty/invoke.kt

@@ -1,7 +1,7 @@
 // WITH_RUNTIME
 // IS_APPLICABLE: false
 class A(val n: Int) {
-    fun <caret>invoke(): Int = 1
+    operator fun <caret>invoke(): Int = 1
 }
 
 fun test(a: A) {