TextEditor: use Utils::FilePath as file member in AssistInterface

Change-Id: I3bf9b013b9350411f918efdb9d1a36a2c22bf972
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/languageclient/client.h

@@ -179,7 +179,7 @@ public:
     HoverHandler *hoverHandler();
     void rehighlight();
 
-    bool documentUpdatePostponed(const QString &fileName) const;
+    bool documentUpdatePostponed(const Utils::FilePath &fileName) const;
 
 signals:
     void initialized(LanguageServerProtocol::ServerCapabilities capabilities);