Remove unused variables

These are left over from the previous sidebar code, which was replaced
recently.

part.cpp

@@ -2246,23 +2246,19 @@ void Part::slotRebuildBookmarkMenu()
 void Part::enableLayers(bool enable)
 {
     if ( !enable ) {
-        m_layersEnabled = false;
         return;
     }
 
     m_sidebar->addItem( m_layers, QIcon::fromTheme( QStringLiteral("format-list-unordered") ), i18n( "Layers" ) );
-    m_layersEnabled = true;
 }
 
 void Part::enableSidebarSignaturesItem( bool enable )
 {
     if ( !enable ) {
-        m_signaturePanelEnabled = false;
         return;
     }
 
     m_sidebar->addItem( m_signaturePanel, QIcon::fromTheme(QStringLiteral("application-pkcs7-signature")), i18n("Signatures") );
-    m_signaturePanelEnabled = true;
 }
 
 void Part::slotShowFindBar()

part.h

@@ -327,9 +327,7 @@ class OKULARPART_EXPORT Part : public KParts::ReadWritePart, public Okular::Docu
         QPointer<Reviews> m_reviewsWidget;
         QPointer<BookmarkList> m_bookmarkList;
         QPointer<Layers> m_layers;
-        bool m_layersEnabled;
         QPointer<SignaturePanel> m_signaturePanel;
-        bool m_signaturePanelEnabled;
 
         // document watcher (and reloader) variables
         KDirWatch *m_watcher;