Delete test case for navigation to 'invoke' of functional type

Classes for functional types will not have any physical source representation
anymore, so navigation to them in the IDE will not be possible

idea/testData/resolve/builtins/function.kt

@@ -1,4 +0,0 @@
-fun f(p : () -> String) {
-    p.<ref>invoke()
-}
-//kotlin/Functions.kt:invoke

idea/tests/org/jetbrains/kotlin/idea/references/BuiltInsReferenceResolverTest.java

@@ -25,8 +25,8 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor;
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
 import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor;
 import org.jetbrains.kotlin.descriptors.impl.DeclarationDescriptorVisitorEmptyBodies;
-import org.jetbrains.kotlin.idea.test.PluginTestCaseBase;
 import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde;
+import org.jetbrains.kotlin.idea.test.PluginTestCaseBase;
 import org.jetbrains.kotlin.test.JetTestUtils;
 
 import java.util.ArrayList;
@@ -50,10 +50,6 @@ public class BuiltInsReferenceResolverTest extends ResolveTestCase {
         doTest();
     }
 
-    public void testFunction() throws Exception {
-        doTest();
-    }
-
     public void testInt() throws Exception {
         doTest();
     }