[NI] Remove lambda coersion to Unit in case of error return type(s)

Coersion to Unit from error type leads to misleading type mismatches:
"expected <expected lambda return type> found Unit", despite no user-provided Unit / empty lambda.
These diagnostics were collected, but not reported before, and that had been disguising the issue for a while.

KT-34729 Fixed

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -14715,11 +14715,6 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
         @TestDataPath("$PROJECT_ROOT")
         @RunWith(JUnit3RunnerWithInners.class)
         public static class NotNullAssertions extends AbstractLightAnalysisModeTest {
-            @TestMetadata("paramAssertionMessage.kt")
-            public void ignoreParamAssertionMessage() throws Exception {
-                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
-            }
-
             private void runTest(String testDataFilePath) throws Exception {
                 KotlinTestUtils.runTest(this::doTest, TargetBackend.JVM, testDataFilePath);
             }
@@ -14808,6 +14803,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/nullableTypeParameter.kt");
             }
 
+            @TestMetadata("paramAssertionMessage.kt")
+            public void testParamAssertionMessage() throws Exception {
+                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
+            }
+
             @TestMetadata("staticCallErrorMessage.kt")
             public void testStaticCallErrorMessage() throws Exception {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/staticCallErrorMessage.kt");