Remove project_shape() prototype (#569)

This function has been removed in favor of `project`, but as @adstraw discovered, its prototype was still lying around the header file, lookin' all smug.

src/ngraph/shape.hpp

@@ -76,5 +76,4 @@ namespace ngraph
 
     inline bool is_scalar(const Shape& shape) { return 0 == shape.size(); }
     inline bool is_vector(const Shape& shape) { return 1 == shape.size(); }
-    Shape project_shape(const Shape& shape, const AxisSet& deleted_axes);
 }