ci(telemetry): only allow get_events to return each event one time

[emmettbutler]

An attempt at a more durable fix for test failures like this one by deduplicating the events returned from test_agent_session.get_events().

Removed assertions are because they don't apply given this fix.

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.
• If change touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Description motivates each change
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Change is maintainable (easy to change, telemetry, documentation)
• Release note makes sense to a user of the library
• Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: emmett.butler/gotten-events
Commit report: 07c7a10
Test service: dd-trace-py

✅ 0 Failed, 77 Passed, 349 Skipped, 45.22s Total duration (41.43s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-04-01 18:22:58

Comparing candidate commit 07c7a10 in PR branch emmett.butler/gotten-events with baseline commit ad2fe25 in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 200 metrics, 9 unstable metrics.

scenario:flasksimple-appsec-telemetry

• 🟥 execution_time [+220.176µs; +267.459µs] or [+3.517%; +4.272%]