[Fir2IR] Don't build overrides for expect classes.

We don't need them except for checking.
And checking doesn't work in any reasonable way anyway.

^KT-65249 Fixed

wasm/wasm.tests/tests-gen/org/jetbrains/kotlin/wasm/test/FirWasmJsCodegenBoxTestGenerated.java

@@ -27364,6 +27364,12 @@ public class FirWasmJsCodegenBoxTestGenerated extends AbstractFirWasmJsCodegenBo
         runTest("compiler/testData/codegen/box/multiplatform/k2/internalOverride2.kt");
       }
 
+      @Test
+      @TestMetadata("kt-65249.kt")
+      public void testKt_65249() {
+        runTest("compiler/testData/codegen/box/multiplatform/k2/kt-65249.kt");
+      }
+
       @Test
       @TestMetadata("mergedOverrides.kt")
       public void testMergedOverrides() {