Don't try to be smart about enabling the Clear Annotation button.

(At a minimum it would need to also handle when the scope changes, but
it's not clear we're adding anything by enabling/disabling it to start
with.)

eeschema/dialogs/dialog_annotate.cpp

@@ -228,7 +228,6 @@ void DIALOG_ANNOTATE::OnApplyClick( wxCommandEvent& event )
     m_MessageWindow->Flush( true );             // Now update to show all messages
     m_Parent->GetCanvas()->Refresh();
 
-    m_btnClear->Enable();
     m_sdbSizer1Cancel->SetDefault();
 
     // Don't close dialog if there are things the user needs to address
@@ -247,7 +246,6 @@ void DIALOG_ANNOTATE::OnApplyClick( wxCommandEvent& event )
 void DIALOG_ANNOTATE::OnClearAnnotationClick( wxCommandEvent& event )
 {
     m_Parent->DeleteAnnotation( GetScope(), GetRecursive() );
-    m_btnClear->Enable( false );
 }