FIR: make declarations marked with 'override' implicitly open

#KT-52236 Fixed

js/js.translator/testData/box/expression/try/overrideThrowableProperties.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_K2: JS_IR
 // EXPECTED_REACHABLE_NODES: 1315
 
 open class Ex0(msg: String, cs: Throwable): Throwable(msg, cs)

js/js.translator/testData/box/native/inheritanceFromNativeTrait.kt

@@ -1,6 +1,5 @@
 // DONT_TARGET_EXACT_BACKEND: WASM
 // WASM_MUTE_REASON: IMPLEMENTING_EXTERNAL_INTERFACE
-// IGNORE_BACKEND_K2: JS_IR
 // EXPECTED_REACHABLE_NODES: 1297
 package foo
 

js/js.translator/testData/box/propertyAccess/configurable.kt

@@ -1,6 +1,5 @@
 // EXPECTED_REACHABLE_NODES: 1345
 // KJS_WITH_FULL_RUNTIME
-// IGNORE_BACKEND_K2: JS_IR
 package foo
 
 external interface EP {

js/js.translator/testData/box/reflection/kClassReifiedWithJsCall.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_K2: JS_IR
 import kotlin.reflect.KClass
 
 // FILE: main.kt

js/js.translator/testData/box/reflection/kClassWithJsCall.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_K2: JS_IR
 // FILE: main.kt
 import kotlin.reflect.KClass
 

js/js.translator/testData/box/reflection/kJsClassWithJsCall.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_K2: JS_IR
 import kotlin.reflect.KClass
 
 // FILE: main.kt

js/js.translator/testData/box/reflection/kTypeWithJsCall.kt

@@ -1,5 +1,4 @@
 // KJS_WITH_FULL_RUNTIME
-// IGNORE_BACKEND_K2: JS_IR
 
 import kotlin.reflect.KClass
 import kotlin.reflect.KType