Kapt tests: minor, add some cases to properties.kt

To check that boolean "is" prefix is treated correctly, and Unit return
type is not translated to void. `@Deprecated` annotations are added just
so that the `$annotations` methods would also be generated.

plugins/kapt3/kapt3-compiler/testData/converter/properties.kt

@@ -11,4 +11,10 @@ class Test {
 
     val constJavaClassValue: Class<*> = String::class.java
     val constClassValue: kotlin.reflect.KClass<*> = (String::class)
+
+    @Deprecated("")
+    var isBoolean = false
+
+    @Deprecated("")
+    var unit = Unit
 }