Change FUNCTION_EXPRESSION_WITH_NAME severity to ERROR

Also drop deprecation related parts and get rid of usages of this `feature` within testData

idea/testData/inspections/cleanup/cleanup.kt

@@ -4,8 +4,6 @@ import pack.oldFun3
 
 class A private()
 
-val x = fun foo(x: String) { }
-
 fun foo() {
     @loop
     for (i in 1..100) {

idea/testData/inspections/cleanup/cleanup.kt.after

@@ -3,8 +3,6 @@ import pack.oldFun2 // should not be removed for non-deprecated overload used
 
 class A private constructor()
 
-val x = fun(x: String) { }
-
 fun foo() {
     loop@
     for (i in 1..100) {