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

compiler/testData/codegen/boxWithJava/reflection/kotlinPropertyInheritedInJava/K.kt

@@ -13,9 +13,9 @@ fun box(): String {
     val prop = J::prop
     if (prop !is KMutableProperty1<*, *>) return "Fail instanceof"
     if (prop.name != "prop") return "Fail name: ${prop.name}"
-    if (prop.get(j) != ":(") return "Fail get before: ${prop[j]}"
-    prop[j] = ":)"
-    if (prop.get(j) != ":)") return "Fail get after: ${prop[j]}"
+    if (prop.get(j) != ":(") return "Fail get before: ${prop.get(j)}"
+    prop.set(j, ":)")
+    if (prop.get(j) != ":)") return "Fail get after: ${prop.get(j)}"
 
 
     if (prop == K::prop) return "Fail J::prop == K::prop (these are different properties)"
@@ -29,7 +29,7 @@ fun box(): String {
     if (prop != prop2) return "Fail: property references from :: and from properties differ: $prop != $prop2"
     if (prop2 !is KMutableProperty1<*, *>) return "Fail instanceof 2"
     (prop2 as KMutableProperty1<J, String>).set(j, "::)")
-    if (prop.get(j) != "::)") return "Fail get after 2: ${prop[j]}"
+    if (prop.get(j) != "::)") return "Fail get after 2: ${prop.get(j)}"
 
 
     val ext = klass.memberExtensionProperties.firstOrNull { it.name == "ext" } ?: "Fail: no 'ext' property in memberExtensionProperties"

compiler/testData/codegen/boxWithJava/reflection/mutatePrivateJavaInstanceField/K.kt

@@ -5,6 +5,6 @@ fun box(): String {
     val a = J()
     val p = J::class.members.single { it.name == "result" } as KMutableProperty1<J, String>
     p.isAccessible = true
-    p[a] = "OK"
-    return p[a]
+    p.set(a, "OK")
+    return p.get(a)
 }

compiler/testData/codegen/boxWithJava/reflection/referenceToJavaFieldOfKotlinSubclass/K.kt

@@ -3,5 +3,5 @@ open class K
 fun box(): String {
     val f = J::value
     val a = J()
-    return if (f.get(a) == 42) "OK" else "Fail: ${f[a]}"
+    return if (f.get(a) == 42) "OK" else "Fail: ${f.get(a)}"
 }