Update avante copilot model to claude 3.7

Author: karolis-vinted

lua/custom/plugins/avante.lua

@@ -6,7 +6,7 @@ return {
     provider = 'copilot',
     copilot = {
       endpoint = 'https://api.githubcopilot.com',
-      model = 'claude-3.5-sonnet',
+      model = 'claude-3.7-sonnet',
       proxy = nil,
       allow_insecure = false,
       timeout = 30000,