Base: modernize C++: return braced init list

src/Base/PrecisionPyImp.cpp

@@ -33,7 +33,7 @@ using Base::PrecisionPy;
 // returns a string which represents the object e.g. when printed in python
 std::string PrecisionPy::representation() const
 {
-    return std::string("<Precision object>");
+    return {"<Precision object>"};
 }
 
 PyObject* PrecisionPy::angular(PyObject *args)