Delete assertion on receiver presence in 'invoke'

#KT-6541 Fixed
 #KT-7383 Fixed

compiler/testData/diagnostics/tests/resolve/invoke/invokeNonExtensionLambdaInContext.kt

@@ -0,0 +1,7 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+class C {
+    fun f() {}
+}
+
+fun C.g(f: (String) -> Unit = { s -> f() }) {}

compiler/testData/diagnostics/tests/resolve/invoke/invokeNonExtensionLambdaInContext.txt

@@ -0,0 +1,11 @@
+package
+
+internal fun C.g(/*0*/ f: (kotlin.String) -> kotlin.Unit = ...): kotlin.Unit
+
+internal final class C {
+    public constructor C()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal final fun f(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}