fix: Memory leak in repo-server

[AJChandler]

This resolves a memory leak in the repo-server during plugin discovery caused by the connection not being closed.

Repo-Server Goroutines Leak

goroutine profile: total 1500
1458 @ 0x474eae 0x450a25 0x23d30ec 0x47d741
#   0x23d30eb   google.golang.org/grpc/internal/grpcsync.(*CallbackSerializer).run+0x10b    /go/pkg/mod/google.golang.org/grpc@v1.66.2/internal/grpcsync/callback_serializer.go:88

Repo-Server Goroutines Leak - Hard Refresh Applications x2

goroutine profile: total 4842
3138 @ 0x474eae 0x450a25 0x23d30ec 0x47d741
#   0x23d30eb   google.golang.org/grpc/internal/grpcsync.(*CallbackSerializer).run+0x10b    /go/pkg/mod/google.golang.org/grpc@v1.66.2/internal/grpcsync/callback_serializer.go:88

Fix Applied - Repo-Server Goroutines Leak - Hard Refresh Applications x2

Introduced by: #20196

Related improvement that would make this class of error harder to occur: #20217

This should be cherry-picked into the v2.13 release.

Checklist:

• [x] Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• [x] The title of the PR states what changed and the related issues number (used for the release note).
• [x] The title of the PR conforms to the Toolchain Guide
• [ ] I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• [ ] I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• [ ] Does this PR require documentation updates?
• [ ] I've updated documentation as required by this PR.
• [x] I have signed off all my commits as required by DCO
• [ ] I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• [x] My build is green (troubleshooting builds).
• [ ] My new feature complies with the feature status guidelines.
• [x] I have added a brief description of why this PR is necessary and/or what this PR solves.
• [ ] Optional. My organization is added to USERS.md.
• [ ] Optional. For bug fixes, I've indicated what older releases this fix should be cherry-picked into (this may or may not happen depending on risk/complexity).

[bunnyshell[bot]]

:x: Preview Environment deleted from Bunnyshell

Available commands (reply to this comment):

• :rocket: /bns:deploy to deploy the environment

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 55.04%. Comparing base (fc9b33b) to head (3b07c91). Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
util/app/discovery/discovery.go	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #20876 +/- ## ========================================== + Coverage 55.00% 55.04% +0.04% ========================================== Files 324 324 Lines 55398 55400 +2 ========================================== + Hits 30471 30497 +26 + Misses 22309 22279 -30 - Partials 2618 2624 +6 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[crenshaw-dev]

/cherry-pick release-2.13