[hotfix][docs] Add avro. prefix for timestamp_mapping.legacy format option key

Author: ferenc-csaky

docs/content.zh/docs/connectors/table/formats/avro.md

@@ -87,7 +87,7 @@ Format 参数
       <td>仅用于 <a href="{{< ref "docs/connectors/table/filesystem" >}}">filesystem</a>，avro 压缩编解码器。默认 snappy 压缩。目前支持：null, deflate、snappy、bzip2、xz。</td>
     </tr>
     <tr>
-      <td><h5>timestamp_mapping.legacy</h5></td>
+      <td><h5>avro.timestamp_mapping.legacy</h5></td>
       <td>可选</td>
       <td style="word-wrap: break-word;">true</td>
       <td>Boolean</td>

docs/content/docs/connectors/table/formats/avro.md

@@ -99,7 +99,7 @@ Format Options
       <td>For <a href="{{< ref "docs/connectors/table/filesystem" >}}">Filesystem</a> only, the compression codec for avro. Snappy compression as default. The valid enumerations are: null, deflate, snappy, bzip2, xz.</td>
     </tr>
     <tr>
-      <td><h5>timestamp_mapping.legacy</h5></td>
+      <td><h5>avro.timestamp_mapping.legacy</h5></td>
       <td>optional</td>
       <td>yes</td>
       <td style="word-wrap: break-word;">true</td>