[FIR] Set FirJavaClass.isInner properly

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/declarations/FirJavaClass.kt

@@ -143,8 +143,9 @@ internal class FirJavaClassBuilder : AbstractFirRegularClassBuilder, FirAnnotati
 
     @OptIn(FirImplementationDetail::class)
     override fun build(): FirJavaClass {
+        val isInner = !isTopLevel && !isStatic
         val status = FirDeclarationStatusImpl(visibility, modality).apply {
-            isInner = !isTopLevel && !isStatic
+            this.isInner = isInner
             isCompanion = false
             isData = false
             isInline = false

compiler/testData/codegen/box/collections/charSequence.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // TARGET_BACKEND: JVM
 
 // FILE: J.java