Removed physac.hpp from the installed files list

The file physac.hpp got removed in
d19cbcc, but remained in
`install/CMakeLists.txt`, causing `cmake --install` to fail.

Author: dk949

include/CMakeLists.txt

@@ -22,7 +22,6 @@ install(FILES
     ModelAnimation.hpp
     Mouse.hpp
     Music.hpp
-    physac.hpp
     Ray.hpp
     RayCollision.hpp
     RaylibException.hpp