Minor: drop obsolete code

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/symbols/IrCallSignature.kt

@@ -1,26 +0,0 @@
-/*
- * Copyright 2010-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.ir.symbols
-
-import org.jetbrains.kotlin.types.KotlinType
-
-interface IrCallSignature {
-    val dispatchReceiverType: KotlinType?
-    val extensionReceiverType: KotlinType?
-    val valueParameterTypes: List<KotlinType>
-    val returnType: KotlinType
-}