Update CODEOWNERS paths for plugins

[khanhtc1202]

What this PR does:

As @mohammedfirdouss noticed me that he didn't have the permission to merge changes in plugins dir even with the plugin team members config, I think it maybe caused by this missing / in the CODEOWNER.

Why we need it:

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 29.37%. Comparing base (cf04ef8) to head (d6b053b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6992   +/-   ##
=======================================
  Coverage   29.37%   29.37%           
=======================================
  Files         601      601           
  Lines       64276    64276           
=======================================
  Hits        18884    18884           
  Misses      43924    43924           
  Partials     1468     1468           

Flag	Coverage Δ
.	23.14% <ø> (ø)
.-pkg-app-pipedv1-plugin-analysis	32.43% <ø> (ø)
.-pkg-app-pipedv1-plugin-ecs	31.74% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	58.37% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	59.66% <ø> (ø)
.-pkg-app-pipedv1-plugin-scriptrun	54.83% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	38.18% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	33.04% <ø> (ø)
.-pkg-app-pipedv1-plugin-waitapproval	52.71% <ø> (ø)
.-pkg-plugin-sdk	50.34% <ø> (ø)
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.51% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[khanhtc1202]

@Warashi @t-kikuc @ffjlabo please approve this change when you have time

[Warashi]

@khanhtc1202
This problem is not caused by the CODEOWNERS file.
We set the branch protection rule to prevent PR merges from anyone except the pipecd-approvers, pipecd-approvers-web, and pipecd-approvers-docs.
The settings are here: "Restrict who can push to matching branches" of https://github.com/pipe-cd/pipecd/settings/branch_protection_rules/16741214