[CI] skip audit on .buildkite dep installation (elastic#239699)

## Summary
We've seen on CI, that the install time for `.buildkite` dependencies
skyrocketed from a 3s install to 7m+.

Local debug runs revealed it's the audit run that takes 7 minutes to
time out, this stalls the finish of the install.
```
npm http fetch POST 503 https://registry.npmjs.org/-/npm/v1/security/audits/quick 120042ms
npm verbose audit error HttpErrorGeneral: 503 Service Unavailable - POST https://registry.npmjs.org/-/npm/v1/security/audits/quick - Service Unavailable
npm verbose audit error     at /usr/local/lib/node_modules/npm/node_modules/npm-registry-fetch/lib/check-response.js:103:15
```
Could be caused by recent AWS outages.

Disabling this auditing doesn't affect CI directly, we can try to turn
this back on later.

Author: delanni

.buildkite/scripts/common/setup_buildkite_deps.sh

@@ -18,5 +18,5 @@ if ! ts-node --version; then
 fi
 
 cd '.buildkite'
-retry 5 15 npm ci
+retry 5 15 npm ci --no-audit
 cd -