[FIR] Do not use strict type equality in override checker

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirStandardOverrideChecker.kt

@@ -31,7 +31,7 @@ class FirStandardOverrideChecker(session: FirSession) : FirAbstractOverrideCheck
             val baseIsFlexible = substitutedBaseType.isFlexible()
             val candidateIsFlexible = substitutedCandidateType.isFlexible()
             if (baseIsFlexible == candidateIsFlexible) {
-                return strictEqualTypes(context, substitutedCandidateType, substitutedBaseType)
+                return AbstractTypeChecker.equalTypes(context, substitutedCandidateType, substitutedBaseType)
             }
             val lowerBound: SimpleTypeMarker
             val upperBound: SimpleTypeMarker

compiler/fir/resolve/testData/resolve/problems/definitelyNotNullAmbiguity.kt

@@ -17,5 +17,5 @@ interface B : A {
 // FILE: main.kt
 
 fun test(visitor: KtVisitor<String, Unit>, element: B) {
-    element.<!AMBIGUITY!>accept<!>(visitor, Unit)
+    element.accept(visitor, Unit)
 }

compiler/fir/resolve/testData/resolve/problems/definitelyNotNullAmbiguity.txt

@@ -5,5 +5,5 @@ FILE: B.kt
     }
 FILE: main.kt
     public final fun test(visitor: R|KtVisitor<kotlin/String, kotlin/Unit>|, element: R|B|): R|kotlin/Unit| {
-        R|<local>/element|.<Ambiguity: accept, [/B.accept, /A.accept]>#(R|<local>/visitor|, Q|kotlin/Unit|)
+        R|<local>/element|.R|/B.accept|<R|kotlin/String|, R|kotlin/Unit|>(R|<local>/visitor|, Q|kotlin/Unit|)
     }