Drop RawTypeMarker as it's effectively unused anymore

See the previous commits

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt

@@ -184,7 +184,7 @@ data class ConeDefinitelyNotNullType(val original: ConeSimpleKotlinType) : ConeS
 class ConeRawType private constructor(
     lowerBound: ConeSimpleKotlinType,
     upperBound: ConeSimpleKotlinType
-) : ConeFlexibleType(lowerBound, upperBound), RawTypeMarker {
+) : ConeFlexibleType(lowerBound, upperBound) {
     companion object {
         fun create(
             lowerBound: ConeSimpleKotlinType,

compiler/resolution.common/src/org/jetbrains/kotlin/types/AbstractTypeApproximator.kt

@@ -143,7 +143,7 @@ abstract class AbstractTypeApproximator(
 
                     val lowerResult = approximateTo(lowerBound, conf, depth)
 
-                    val upperResult = if (type !is RawTypeMarker && lowerBound.typeConstructor() == upperBound.typeConstructor())
+                    val upperResult = if (!type.isRawType() && lowerBound.typeConstructor() == upperBound.typeConstructor())
                         lowerResult?.withNullability(upperBound.isMarkedNullable())
                     else
                         approximateTo(upperBound, conf, depth)

core/compiler.common/src/org/jetbrains/kotlin/types/model/TypeSystemContext.kt

@@ -23,7 +23,6 @@ interface DefinitelyNotNullTypeMarker : SimpleTypeMarker
 
 interface FlexibleTypeMarker : KotlinTypeMarker
 interface DynamicTypeMarker : FlexibleTypeMarker
-interface RawTypeMarker : FlexibleTypeMarker
 interface StubTypeMarker : SimpleTypeMarker
 
 interface TypeArgumentListMarker

core/descriptors/src/org/jetbrains/kotlin/types/RawType.kt

@@ -16,6 +16,4 @@
 
 package org.jetbrains.kotlin.types
 
-import org.jetbrains.kotlin.types.model.RawTypeMarker
-
-interface RawType : RawTypeMarker
+interface RawType