[MPP] workaround inc/dec operator checks in expect classes

Implicit receiver type inside expect class is inconsistent with the
type resolved from an explicit reference inside that class. The former
one is a default class type, i.e. expect; the latter one resolves to
an actual type when either expect and actual are in the same module, or
when the sources are compiled for a particular platform.

The workaround is to manually actualize implicit receiver type for one
particular check affected by the broken subtyping.

KT-49714

compiler/testData/diagnostics/tests/IncDecOperatorsInExpectClass.kt

@@ -1,10 +1,11 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +MultiPlatformProjects
 // SKIP_TXT
 // Issue: KT-49714
 
 expect class Counter {
-    <!INAPPLICABLE_OPERATOR_MODIFIER!>operator<!> fun inc(): Counter
-    <!INAPPLICABLE_OPERATOR_MODIFIER!>operator<!> fun dec(): Counter
+    operator fun inc(): Counter
+    operator fun dec(): Counter
 }
 
 actual typealias Counter = Int