[FIR] Use ConeKotlinType to represent vararg's element type

We are using `ConeKotlinType` instead of `FirTypeRef` to represent
that element type of vararg doesn't have any source. It has a type
that was inferred. If we try to specify a source, then we could
end up with the incorrect place for diagnostic.

#KT-59682 Fixed

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/javaAnnotationsMapping.kt

@@ -222,9 +222,7 @@ private fun List<JavaAnnotationArgument>.mapJavaTargetArguments(session: FirSess
             ConeAttributes.Empty
         )
         coneTypeOrNull = elementConeType
-        varargElementType = buildResolvedTypeRef {
-            type = elementConeType.createOutArrayType()
-        }
+        coneElementTypeOrNull = elementConeType.createOutArrayType()
     }
 }