Update __init__.py

Update sdl2_ttf to version 2.0.15

Author: Neizvestnyj

pythonforandroid/recipes/sdl2_ttf/__init__.py

@@ -2,7 +2,7 @@
 
 
 class LibSDL2TTF(BootstrapNDKRecipe):
-    version = '2.0.14'
+    version = '2.0.15'
     url = 'https://www.libsdl.org/projects/SDL_ttf/release/SDL2_ttf-{version}.tar.gz'
     dir_name = 'SDL2_ttf'