Fix potential race condition in PolicyEngineTest#notificationTest

[nscuro]

Description

Fixes potential race condition in PolicyEngineTest#notificationTest.

Since notification dispatch happens asynchronously, it's possible that the assertion happens before the notification is received. Await notifications with a small timeout instead.

Addressed Issue

N/A

Additional Details

Example test failure: https://github.com/DependencyTrack/dependency-track/actions/runs/11124919968/job/30911500389#step:4:486

Checklist

• I have read and understand the contributing guidelines
• This PR fixes a defect, and I have provided tests to verify that the fix is effective
• This PR implements an enhancement, and I have provided tests to verify that it works as intended
• This PR introduces changes to the database model, and I have added corresponding update logic
• This PR introduces new or alters existing behavior, and I have updated the documentation accordingly

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 56d9deb1	✅ ∅ (target: 70.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (56d9deb)	Report Missing	Report Missing	Report Missing
Head commit (b4ec664)	22436	17743	79.08%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#4203)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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Footnotes

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