Reset open_target in acceptNavigationRequest.

After ddb39275eb, when something was opened via
hints in a new tab, the open_target still was set afterwards and the next
regular open did open in a new tab.

qutebrowser/browser/webpage.py

@@ -514,6 +514,7 @@ class BrowserPage(QWebPage):
         tabbed_browser = objreg.get('tabbed-browser', scope='window',
                                     window=self._win_id)
         open_target = self.view().open_target
+        self.view().open_target = usertypes.ClickTarget.normal
         if open_target == usertypes.ClickTarget.tab:
             tabbed_browser.tabopen(url, False)
             return False