Utils: Remove FilePath::operator+()

This was a alias for .stringAppended(), but can be used too easily
when .pathAppended() is meant.

Change-Id: Ia3b64d39828d4074b43d87c923ce3a6a87038948
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/qmakeprojectmanager/qmakeproject.cpp

@@ -1376,7 +1376,8 @@ void QmakeBuildSystem::collectLibraryData(const QmakeProFile *file, DeploymentDa
                 targetFileName += QLatin1Char('.');
                 while (!versionComponents.isEmpty()) {
                     const QString versionString = versionComponents.join(QLatin1Char('.'));
-                    deploymentData.addFile(destDirFor(ti) / targetFileName + versionString,
+                    deploymentData.addFile(destDirFor(ti).pathAppended(targetFileName
+                                                                       + versionString),
                                            targetPath);
                     versionComponents.removeLast();
                 }