CBG-4902: Fix Flaky Test TestBlipOneShotChangesSubscription

[RIT3shSapata]

CBG-4902

Describe your PR here...

• The NumPullReplActiveOneShot's decrement is deferred, so updated the require condition to wait for the metric to be eventually updated to the desired value

Pre-review checklist

• Removed debug logging (fmt.Print, log.Print, ...)
• Logging sensitive data? Make sure it's tagged (e.g. base.UD(docID), base.MD(dbName))
• Updated relevant information in the API specifications (such as endpoint descriptions, schemas, ...) in docs/api

Dependencies (if applicable)

• Link upstream PRs
• Update Go module dependencies when merged

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGatewayIntegration/0000/

[Copilot]

Pull Request Overview

This PR fixes a flaky test TestBlipOneShotChangesSubscription by addressing a timing issue with metric updates. The test was failing because it was checking for an immediate value of a metric that gets decremented asynchronously.

• Updated the test assertion to wait for the NumPullReplActiveOneShot metric to eventually reach the expected value