Remove redundant receiver in "Change function signature" quick fix

So #KT-12298 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/ChangeMemberFunctionSignatureFix.kt

@@ -42,6 +42,7 @@ import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.KtNamedFunction
 import org.jetbrains.kotlin.psi.KtParameterList
 import org.jetbrains.kotlin.psi.KtPsiFactory
+import org.jetbrains.kotlin.psi.typeRefHelpers.setReceiverTypeReference
 import org.jetbrains.kotlin.renderer.ClassifierNamePolicy
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.resolve.descriptorUtil.setSingleOverridden
@@ -330,6 +331,9 @@ class ChangeMemberFunctionSignatureFix private constructor(
                 }
 
                 val newParameterList = function.valueParameterList!!.replace(patternFunction.valueParameterList!!) as KtParameterList
+                if (patternFunction.receiverTypeReference == null && function.receiverTypeReference != null) {
+                    function.setReceiverTypeReference(null)
+                }
                 ShortenReferences.DEFAULT.process(newParameterList)
             }
         }

idea/testData/quickfix/override/nothingToOverride/removeFunctionReciever.kt

@@ -0,0 +1,8 @@
+// "Change function signature to 'fun x(s: String)'" "true"
+open class A {
+    open fun x(s: String) {}
+}
+
+class B : A() {
+    <caret>override fun String.x() {}
+}

idea/testData/quickfix/override/nothingToOverride/removeFunctionReciever.kt.after

@@ -0,0 +1,8 @@
+// "Change function signature to 'fun x(s: String)'" "true"
+open class A {
+    open fun x(s: String) {}
+}
+
+class B : A() {
+    <caret>override fun x(s: String) {}
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -8362,6 +8362,11 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
                 runTest("idea/testData/quickfix/override/nothingToOverride/overrideJavaMethod.kt");
             }
 
+            @TestMetadata("removeFunctionReciever.kt")
+            public void testRemoveFunctionReciever() throws Exception {
+                runTest("idea/testData/quickfix/override/nothingToOverride/removeFunctionReciever.kt");
+            }
+
             @TestMetadata("removeOverride.kt")
             public void testRemoveOverride() throws Exception {
                 runTest("idea/testData/quickfix/override/nothingToOverride/removeOverride.kt");