fix(toolkit-lib): join dynamic values with spaces instead of commas

[snese]

Issue

Closes aws/aws-cdk#31963

Reason for this change

The addDynamicValues method in NoticesFilter joins multiple dynamic values with commas, producing invalid cdk bootstrap commands like:

cdk bootstrap aws://ACCOUNT/us-east-1,aws://ACCOUNT/us-west-2

Running this command fails with:

Expected environment name in format 'aws://<account>/<region>'

Description of changes

Changed the join separator from , to (space) in addDynamicValues() so the suggested command is valid:

cdk bootstrap aws://ACCOUNT/us-east-1 aws://ACCOUNT/us-west-2

Also updated two JSDoc comments that referenced the old comma separator.

Description of how you validated changes

• All 55 existing unit tests in notices.test.ts pass
• Updated the test assertion that verified comma-separated output to expect space-separated output
• ESLint and TypeScript compilation clean

Checklist

• My code adheres to the CONTRIBUTING GUIDE
• If my change affects existing tests, I have updated those tests accordingly

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.79%. Comparing base (69089a7) to head (d50de47).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1219      +/-   ##
==========================================
- Coverage   87.87%   87.79%   -0.08%     
==========================================
  Files          73       73              
  Lines       10168    10168              
  Branches     1348     1343       -5     
==========================================
- Hits         8935     8927       -8     
- Misses       1209     1217       +8     
  Partials       24       24              

Flag	Coverage Δ
suite.unit	87.79% <ø> (-0.08%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 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.