Fix coercion to Unit when variable already have other constraints

Don't add `Unit` if variable has an upper constraint T <: A.

 It's impossible to coerce variable T to Unit as constraint system will
 be always contradictory: T := Unit => Unit should be subtype of A

 #KT-39900 Fixed

compiler/testData/diagnostics/tests/inference/coercionToUnit/coercionWithExpectedTypeAndBound.kt

@@ -3,11 +3,11 @@
 fun <T : Number> materializeNumber(): T = TODO()
 
 fun a(): Unit = run {
-    <!OI;TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>materializeNumber<!>()
+    <!NI;NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER, OI;TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>materializeNumber<!>()
 }
 
 fun b(): Unit = run {
     run {
-        <!OI;TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>materializeNumber<!>()
+        <!NI;NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER, OI;TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>materializeNumber<!>()
     }
 }

compiler/testData/diagnostics/tests/inference/coercionToUnit/coerctionToUnitForATypeWithUpperBound.kt

@@ -0,0 +1,15 @@
+// FIR_IDENTICAL
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface Base
+class Foo : Base
+
+fun <T : Base> myRun(action: () -> T): T = action()
+
+fun foo(f: (Foo) -> Unit) {}
+
+fun main() {
+    foo { f: Foo ->
+        myRun { f }
+    }
+}

compiler/testData/diagnostics/tests/inference/coercionToUnit/coerctionToUnitForATypeWithUpperBound.txt

@@ -0,0 +1,18 @@
+package
+
+public fun foo(/*0*/ f: (Foo) -> kotlin.Unit): kotlin.Unit
+public fun main(): kotlin.Unit
+public fun </*0*/ T : Base> myRun(/*0*/ action: () -> T): T
+
+public interface Base {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Foo : Base {
+    public constructor Foo()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}