Fix infinite recursion in GLES2 _copy_texscreen

Bug introduced in 9430e68cf3013aaa0673a4dfff844324a9c1274a,
likely a typo.

drivers/gles2/rasterizer_canvas_gles2.cpp

@@ -1227,7 +1227,7 @@ void RasterizerCanvasGLES2::_copy_texscreen(const Rect2 &p_rect) {
 
 	state.canvas_texscreen_used = true;
 
-	_copy_texscreen(p_rect);
+	_copy_screen(p_rect);
 
 	// back to canvas, force rebind
 	state.using_texture_rect = false;