FIR: skip return insertion for lambda w/ Unit return type

compiler/testData/ir/irText/types/coercionToUnitInLambdaReturnValue.fir.txt

@@ -1,12 +0,0 @@
-FILE fqName:<root> fileName:/coercionToUnitInLambdaReturnValue.kt
-  FUN name:use visibility:public modality:FINAL <> (fn:kotlin.Function0<kotlin.Unit>) returnType:kotlin.Unit
-    VALUE_PARAMETER name:fn index:0 type:kotlin.Function0<kotlin.Unit>
-    BLOCK_BODY
-  FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Unit
-    BLOCK_BODY
-      CALL 'public final fun use (fn: kotlin.Function0<kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
-        fn: FUN_EXPR type=kotlin.Function0<kotlin.Unit> origin=LAMBDA
-          FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Unit
-            BLOCK_BODY
-              RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Unit declared in <root>.test'
-                CONST Int type=kotlin.Int value=42

compiler/testData/ir/irText/types/coercionToUnitInLambdaReturnValue.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +NewInference
 
 fun use(fn: () -> Unit) {}