[BugFix] Fix a typo in class StarRocksDynamicSinkFunction

[jiandongchen]

What type of PR is this：

• [ ] BugFix
• [ ] Feature
• [ ] Enhancement
• [ ] Refactor
• [ ] UT
• [x] Doc
• [ ] Tool

Which issues of this PR fixes ：

Fix a typo in class StarRocksDynamicSinkFunction, which should be fulfill instead of fullfill.

Problem Summary(Required) ：

Checklist:

• [ ] I have added test cases for my bug fix or my new feature
• [ ] This pr will affect users' behaviors
• [ ] This pr needs user documentation (for new or modified features or behaviors)
• [ ] I have added documentation for my new feature or new function

[CLAassistant]

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