fix(server): wrong env variable condition in nginx conf (#8084)

Author: Brooooooklyn

.github/deployment/front/nginx.conf

@@ -14,7 +14,7 @@ http {
   include /etc/nginx/conf.d/*.conf;
 
   map "${AFFINE_ENV}" $mobile_root {
-    canary /app/mobile/;
+    dev /app/mobile/;
     default /app/dist/;
   }
 }