fix: make enable_meta_sniffer behavior consistent with CUSTOM_FALLBACK_FILTER

CUSTOM_FALLBACK_FILTER and ENABLE_META_SNIFFER have the same frontend interaction:
both use a checkbox to control whether to use YAML custom config.

However, their default behaviors are inconsistent when unchecked:
- CUSTOM_FALLBACK_FILTER=0: respects YAML config
- ENABLE_META_SNIFFER=0: forces sniffer to be disabled

This fix makes them consistent: when unchecked, always respect the YAML config file settings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Patrick Gu

luci-app-openclash/root/usr/share/openclash/yml_change.sh

@@ -501,7 +501,7 @@ begin
                Value['sniffer'].merge!(custom_sniffer['sniffer']) if custom_sniffer && custom_sniffer['sniffer']
             end
          else
-            Value['sniffer']['enable'] = false if Value.key?('sniffer')
+            # enable_sniffer 未勾选时，保留原始配置文件中的 sniffer 设置
          end
 
          if en_mode_tun != '0' || ['2', '3'].include?(ipv6_mode)