egl: Don't change context when deleting current.

If we change the current context behind the app's back, those tracking
the current context to minimize context changes are going to get
confused.

This brings the EGL backend in line with the GLX one.

Fixes Bugzilla #4199.

src/video/SDL_egl.c

@@ -825,7 +825,6 @@ SDL_EGL_DeleteContext(_THIS, SDL_GLContext context)
     }
     
     if (egl_context != NULL && egl_context != EGL_NO_CONTEXT) {
-        SDL_EGL_MakeCurrent(_this, NULL, NULL);
         _this->egl_data->eglDestroyContext(_this->egl_data->egl_display, egl_context);
     }