fix apple-touch-icon, regenerate images (#10065)

* fix apple-touch-icon, regenerate images

Fixed semi-transparent pixels of apple-touch-icon.png.

I had to manually exclude public/img/loading.png from the commit because
it's an APNG and one of the tools destroys the animation.

* exclude loading.png

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

Makefile

@@ -550,10 +550,10 @@ generate-images:
 	convert $(TMPDIR)/images/16.png $(TMPDIR)/images/32.png \
 					$(TMPDIR)/images/64.png $(TMPDIR)/images/128.png \
 					$(PWD)/public/img/favicon.ico
-	convert $(PWD)/public/img/favicon.png -fill white -opaque none $(PWD)/public/img/apple-touch-icon.png
-					
+	convert -flatten $(PWD)/public/img/favicon.png $(PWD)/public/img/apple-touch-icon.png
+
 	rm -rf $(TMPDIR)/images
-	$(foreach file, $(shell find public/img -type f -name '*.png'),zopflipng -m -y $(file) $(file);)
+	$(foreach file, $(shell find public/img -type f -name '*.png' ! -name 'loading.png'),zopflipng -m -y $(file) $(file);)
 
 .PHONY: pr
 pr: