[Hotfix] Ensure install-plugin.sh compatibility with sh on Debian #5630

[yanxiaole]

Purpose of this pull request

This PR remedies the "Bad substitution" error encountered when executing install-plugin.sh under dash on Debian systems.
Fixes #5630

Does this PR introduce any user-facing change?

No

How was this patch tested?

manually run sh bin/install-plugin.sh 2.3.3

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 you are contributing the connector code, please check that the following files are updated:
  1. Update change log that in connector document. For more details you can refer to connector-v2
  2. Update plugin-mapping.properties and add new connector information in it
  3. Update the pom file of seatunnel-dist
• Update the release-note.

[Hisoka-X]

Cool! Could you open CI in your fork repository?

[yanxiaole]

Cool! Could you open CI in your fork repository?

enabled, how can I trigger it?

[Hisoka-X]

Cool! Could you open CI in your fork repository?

enabled, how can I trigger it?

add some empty commit

[yanxiaole]

Cool! Could you open CI in your fork repository?

enabled, how can I trigger it?

add some empty commit

done

[Hisoka-X]

cc @EricJoy2048

[Hisoka-X]

Thanks @yanxiaole .