[FIR] Cleanup: drop AMBIGUOUS_ACTUALS diagnostic from the frontend

Motivation: AMBIGUOUS_ACTUALS can't be reported on frontend (because it
requires expect to actual mapping, but the mapping is only available on
backend)

In scope of KT-59938
Review: https://jetbrains.team/p/kt/reviews/13760

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -3779,16 +3779,6 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
-    add(FirErrors.AMBIGUOUS_ACTUALS) { firDiagnostic ->
-        AmbiguousActualsImpl(
-            firSymbolBuilder.buildSymbol(firDiagnostic.a),
-            firDiagnostic.b.map { firBasedSymbol ->
-                firSymbolBuilder.buildSymbol(firBasedSymbol)
-            },
-            firDiagnostic as KtPsiDiagnostic,
-            token,
-        )
-    }
     add(FirErrors.AMBIGUOUS_EXPECTS) { firDiagnostic ->
         AmbiguousExpectsImpl(
             firSymbolBuilder.buildSymbol(firDiagnostic.a),

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -2642,12 +2642,6 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         val compatibility: Map<ExpectActualCompatibility<FirBasedSymbol<*>>, List<KtSymbol>>
     }
 
-    interface AmbiguousActuals : KtFirDiagnostic<KtNamedDeclaration> {
-        override val diagnosticClass get() = AmbiguousActuals::class
-        val declaration: KtSymbol
-        val candidates: List<KtSymbol>
-    }
-
     interface AmbiguousExpects : KtFirDiagnostic<KtNamedDeclaration> {
         override val diagnosticClass get() = AmbiguousExpects::class
         val declaration: KtSymbol

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -3183,13 +3183,6 @@ internal class ActualWithoutExpectImpl(
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<KtNamedDeclaration>(firDiagnostic, token), KtFirDiagnostic.ActualWithoutExpect
 
-internal class AmbiguousActualsImpl(
-    override val declaration: KtSymbol,
-    override val candidates: List<KtSymbol>,
-    firDiagnostic: KtPsiDiagnostic,
-    token: KtLifetimeToken,
-) : KtAbstractFirDiagnostic<KtNamedDeclaration>(firDiagnostic, token), KtFirDiagnostic.AmbiguousActuals
-
 internal class AmbiguousExpectsImpl(
     override val declaration: KtSymbol,
     override val modules: List<FirModuleData>,