Only show relevant widgets on the export dialog

Only show widgets on the export dialog that are relevant to the selected
file format (Wave/Ogg):
* Sample rate is always shown.
* Bit depth settings are only shown when Wave is selected.
* Bit rate settings are only shown when Ogg is selected.

Remove the label that informs the user that not all settings apply to
all export formats as it is not needed anymore. The english text of that
label was: "Please note that not all of the parameters above apply for
all file formats."

include/ExportProjectDialog.h

@@ -53,6 +53,8 @@ private slots:
 	void accept();
 	void startExport();
 
+	void onFileFormatChanged(int);
+
 private:
 	QString m_fileName;
 	QString m_dirName;