[Bug][file base] Csv header fixed ‘,’

[jiamin13579]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If necessary, please update incompatible-changes.md to describe the incompatibility caused by this PR.
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[zhangshenghang]

Please add a test class

[chl-wxp]

Very good pr, this bug is very hidden, thanks for pointing it out.

[LiJie20190102]

Please add a test class

+1, I noticed that the example of e2e uses ','. You can add another delimiter, such as ";"

[jiamin13579]

Please add a test class

+1, I noticed that the example of e2e uses ','. You can add another delimiter, such as ";"

Thanks, added