Remove notifier signals for spellchecking support

The rest of the spellchecking support was removed with d364c05d

.
These notifier signals were left behind, and caused them to be
documented.

Related documentation warnings:
  qquickwebengineprofile.h:144: warning: No documentation for 'QQuickWebEngineProfile::spellCheckLanguageChanged()'
  qquickwebengineprofile.h:145: warning: No documentation for 'QQuickWebEngineProfile::spellCheckEnabledChanged()'

Change-Id: I3b03f3f22ed984d55c09d6e42a258f961c42c584
Reviewed-by: Michal Klocek <michal.klocek@theqtcompany.com>

src/webengine/api/qquickwebengineprofile.h

@@ -141,8 +141,6 @@ Q_SIGNALS:
     void persistentCookiesPolicyChanged();
     void httpCacheMaximumSizeChanged();
     Q_REVISION(1) void httpAcceptLanguageChanged();
-    Q_REVISION(2) void spellCheckLanguageChanged();
-    Q_REVISION(2) void spellCheckEnabledChanged();
 
     void downloadRequested(QQuickWebEngineDownloadItem *download);
     void downloadFinished(QQuickWebEngineDownloadItem *download);