Fix sparkle feed url

Author: intitni

Config.xcconfig

@@ -3,5 +3,5 @@ SLASH = /
 
 BUNDLE_IDENTIFIER_BASE = com.intii.CopilotForXcode
 EXTENSION_BUNDLE_NAME = Copilot
-SPARKLE_FEED_URL = https:$(SLASH)$(SLASH)github.com/intitni/CopilotForXcode/blob/main/appcast.xml
+SPARKLE_FEED_URL = https:$(SLASH)$(SLASH)raw.githubusercontent.com/intitni/CopilotForXcode/main/appcast.xml
 SPARKLE_PUBLIC_KEY = WDzm5GHnc6c8kjeJEgX5GuGiPpW6Lc/ovGjLnrrZvPY=