fix: fix parsing of nested sealed interfaces and classes

[clementdessoude]

What changed with this PR:

Example

Fix parsing of sealed/non-sealed classes & interfaces in an interface's body

Example

public interface Test {
    sealed interface Inner {}

    public static sealed abstract class SealedParent {}

    non-sealed interface Inner {}

    public static non-sealed abstract class SealedParent {}

    final static class SealedChild extends SealedParent {}
}

Relative issues or prs:

Fix #533