Use embed for pixel so it is a proper png file (#4106)

Author: scr-oath

util/httputil/pixel.go

@@ -1,16 +1,15 @@
 package httputil
 
+import _ "embed"
+
 type Pixel struct {
 	Content     []byte
 	ContentType string
 }
 
+//go:embed pixel.png
+var pixelContent []byte
 var Pixel1x1PNG = Pixel{
-	Content: []byte{0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49, 0x48, 0x44,
-		0x52, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x08, 0x06, 0x00, 0x00, 0x00, 0x1F, 0x15, 0xC4,
-		0x89, 0x00, 0x00, 0x00, 0x04, 0x73, 0x42, 0x49, 0x54, 0x08, 0x08, 0x08, 0x08, 0x7C, 0x08, 0x64, 0x88,
-		0x00, 0x00, 0x00, 0x0D, 0x49, 0x44, 0x41, 0x54, 0x08, 0x99, 0x63, 0x60, 0x60, 0x60, 0x60, 0x00, 0x00,
-		0x00, 0x05, 0x00, 0x01, 0x87, 0xA1, 0x4E, 0xD4, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE,
-		0x42, 0x60, 0x82},
+	Content:     pixelContent,
 	ContentType: "image/png",
 }