[Snyk] Security upgrade koa-mount from 3.0.0 to 4.0.0

[snyk-bot]

Snyk has created this PR to fix one or more vulnerable packages in the `yarn` dependencies of this project.

Changes included in this PR

• Changes to the following files to upgrade the vulnerable dependencies to a fixed version:
  • lib/vscode/test/ui/splitview/package.json

⚠️ Warning

Failed to update the yarn.lock, please update manually before merging.

Vulnerabilities that will be fixed

With an upgrade:

Severity	Priority Score (*)	Issue	Breaking Change	Exploit Maturity
	461/1000 Why? Recently disclosed, Has a fix available, CVSS 3.5	Regular Expression Denial of Service (ReDoS) SNYK-JS-DEBUG-3227433	Yes	No Known Exploit

(*) Note that the real score may have changed since the PR was raised.

Check the changes in this PR to ensure they won't cause issues with your project.

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Learn how to fix vulnerabilities with free interactive lessons:

🦉 Regular Expression Denial of Service (ReDoS)

[github-actions]

Scan Summary

Tool	Critical	High	Medium	Low	Status
Dependency Scan (nodejs)	1	3	2	3	❌
Security Audit for Infrastructure	0	1	0	10	✅
Shell Script Analysis	0	0	0	0	✅
Secrets Audit	0	5	0	0	❌

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