update NEWS.md

Author: ufechner7

NEWS.md

@@ -2,7 +2,7 @@
 This project is based on version 1.0 of the Python project [Vortex-Step-Method](https://github.com/ocayon/Vortex-Step-Method)
 
 ## Noteworthy Differences
-- implemented in Julia, therefore about 20 times faster
+- implemented in Julia, therefore about 50 times faster
 - an importer for `.obj` wing geometry files was added (see: [#10](https://github.com/Albatross-Kite-Transport/VortexStepMethod.jl/issues/10))
 - automatic creation of polars using Xfoil.jl was added (see: [#43](https://github.com/Albatross-Kite-Transport/VortexStepMethod.jl/pull/43))
 - a ram-air kite example was added