[all-open] Don't affect private declarations to change their modality to open

plugins/allopen/allopen-cli/testData/bytecodeListing/privateMembers.kt

@@ -13,4 +13,6 @@ private class Test {
 
     internal fun internalMethod() {}
     internal val internalProp: String = ""
+
+    private tailrec fun privateTailrecMethod() {}
 }

plugins/allopen/allopen-cli/testData/bytecodeListing/privateMembers.txt

@@ -6,7 +6,7 @@ public annotation class AllOpen {
 
 @AllOpen
 @kotlin.Metadata
-class Test {
+final class Test {
     // source: 'privateMembers.kt'
     private final @org.jetbrains.annotations.NotNull field internalProp: java.lang.String
     private final field privateProp: java.lang.String
@@ -17,7 +17,8 @@ class Test {
     protected @org.jetbrains.annotations.NotNull method getProtectedProp(): java.lang.String
     public @org.jetbrains.annotations.NotNull method getPublicProp(): java.lang.String
     public method internalMethod$test_module(): void
-    private method privateMethod(): void
+    private final method privateMethod(): void
+    private final method privateTailrecMethod(): void
     protected method protectedMethod(): void
     public method publicMethod(): void
 }