deps: update go-plugin

[tgross]

When Nomad clients built on Go >=1.23 are restarted, the go-plugin client starts leaking a pidfd file handle 1/sec when polling for the plugin server. Long-term we should look at this polling behavior in more detail in the library because the pidfd may let us track the plugin status without polling. But in the meantime the leaking pidfd has been fixed upstream and we should pull that in.

Ref: hashicorp/go-plugin#378
Fixes: #27847

Testing and Reproduction Steps

Run any job and then restart the client agent. (Note this requires running not-in--dev mode.) Using this little script:

#!/usr/bin/env bash

while :
do
    ls /proc/$1/fd/ | wc -l
    sleep 1
done

We see that before the patch, the number of open file handles increases after restarting Nomad. After the patch, it does not.

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and
  ensure regressions will be caught.
• Documentation n/a

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Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

[jrasell]

LGTM, thanks @tgross!

[tgross]

Oops, forgot to go mod tidy there. Fixed