[beatreceiver] Remove exception for packetbeat when setting shutdown_timeout

[khushijain21]

Proposed commit message

We did not set shutdown_timeout field on packetbeat receiver as it had a different semantic meaning. See issue #52005

But this has been fixed in #52005, hence removing this exception

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)
• /test : Run the Buildkite pipeline.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @khushijain21? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[infra-vault-gh-plugin-prod]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[belimawr]

@khushijain21 the tests are failing because shutdown_timeout is now set for Packetbeat. Could you take a look and update the tests?