Add Explanation for entering the API key when adding an LLM (#2055)

### What problem does this PR solve?

Add Explanation for entering the API key when adding an LLM

### Type of change

- [x] Performance Improvement

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Co-authored-by: Zhedong Cen <cenzhedong2@126.com>

web/src/locales/en.ts

       modelsToBeAdded: 'Models to be added',
       addTheModel: 'Add the model',
       apiKey: 'API-Key',
-      apiKeyMessage: 'Please input api key!',
+      apiKeyMessage:
+        'Please enter the API key (for locally deployed model,ignore this).',
       apiKeyTip:
         'The API key can be obtained by registering the corresponding LLM supplier.',
       showMoreModels: 'Show more models',

web/src/locales/zh-traditional.ts

       modelsToBeAdded: '待添加的模型',
       addTheModel: '添加模型',
       apiKey: 'api-key',
-      apiKeyMessage: '請輸入 api key!',
+      apiKeyMessage: '請輸入api key（如果是本地部署的模型，請忽略它）',
       apiKeyTip: 'API key可以通過註冊相應的LLM供應商來獲取。',
       showMoreModels: '展示更多模型',
       baseUrl: 'base-url',

web/src/locales/zh.ts

       modelsToBeAdded: '待添加的模型',
       addTheModel: '添加模型',
       apiKey: 'API-Key',
-      apiKeyMessage: '请输入 api key!',
+      apiKeyMessage: '请输入api key（如果是本地部署的模型，请忽略它）',
       apiKeyTip: 'API key可以通过注册相应的LLM供应商来获取。',
       showMoreModels: '展示更多模型',
       baseUrl: 'Base-Url',