Remove uses of deprecated QProcess::error signal

This overload of error is deprecated in 5.6.

Replace with errorOccurred, which was introduced in 5.6.

Change-Id: Iccfba7e7103b7ce377471696f1f2ec217e52c840
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/qtcprocess.cpp

@@ -739,7 +739,7 @@ void QtcProcess::start()
             setErrorString(tr("Error in command line."));
             // Should be FailedToStart, but we cannot set the process error from the outside,
             // so it would be inconsistent.
-            emit error(QProcess::UnknownError);
+            emit errorOccurred(QProcess::UnknownError);
             return;
         }
         QProcess::start(command, arguments.toUnixArgs());