Upgrade formatting to clang-format 10 (#5895)

* Update formatting tools to clang-format-10

* Reformat using clang-format-10.0.09

src/engine/douglas_peucker.cpp

@@ -119,5 +119,5 @@ std::vector<util::Coordinate> douglasPeucker(std::vector<util::Coordinate>::cons
 
     return simplified_geometry;
 }
-} // ns engine
-} // ns osrm
+} // namespace engine
+} // namespace osrm