GH-285: [Dev] Remove wrong or unnecessary workflow files from arrow-site

[raulcd]

As discussed on #285 currently we don't check the PR titles nor use the merge script.
We could implement some PR checker but if we take a look on the Closed PRs almost none of them are following the structure and we don't seem to use the merge script at all and always use the merge button.

At this point I would propose to just remove this files.

Closes #285

[github-actions]

Thanks for opening a pull request!

Could you open an issue for this pull request on JIRA?
https://issues.apache.org/jira/browse/ARROW

Then could you also rename pull request title in the following format?

ARROW-${JIRA_ID}: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - How to contribute patches

[kou]

+1

Could you ask INFRA to change the default merge message to "Pull request title and description" before we merge this?
See also: https://github.blog/changelog/2022-08-23-new-options-for-controlling-the-default-commit-message-when-merging-a-pull-request/

[raulcd]

Could you ask INFRA to change the default merge message to "Pull request title and description" before we merge this?

Requested here: https://issues.apache.org/jira/browse/INFRA-24122

[jorisvandenbossche]

Thanks!

(the setting is already applied)