refactor: Remove default value for Waline recaptchaV3Key

- Remove 'wasd' as the default value for recaptchaV3Key in Waline config
- Enhance security by not exposing a potentially sensitive key in config

_config.yml

@@ -348,7 +348,7 @@ comment:
       serverUrl: https://example.example.com # Waline server URL. e.g. https://example.example.com
       lang: zh-CN # Waline language. e.g. zh-CN, en-US. See https://waline.js.org/guide/client/i18n.html
       emoji: [] # Waline emojis, see https://waline.js.org/guide/features/emoji.html
-      recaptchaV3Key: wasd # Google reCAPTCHA v3 key. See https://waline.js.org/reference/client/props.html#recaptchav3key
+      recaptchaV3Key: # Google reCAPTCHA v3 key. See https://waline.js.org/reference/client/props.html#recaptchav3key
       turnstileKey: # Turnstile key. See https://waline.js.org/reference/client/props.html#turnstilekey
       reaction: false # Waline reaction. See https://waline.js.org/reference/client/props.html#reaction
     # Gitalk comment system. See https://github.com/gitalk/gitalk