Remove Playwright e2e test from Observability

[CoenWarmer]

Resolves #153884

📝 Summary

The Synthetics team placed E2E testing library Playwright inside the Observability app, to test the Exploratory View route.

Now that the Exploratory View route is placed in its own application, this E2E suite is no longer needed as the Obs team uses the FTR suite for end to end testing.

✅ Acceptance Criteria

• E2E setup inside Obs is removed
• CI definitions updated

[apmmachine]

🤖 GitHub comments

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
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[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[jbudz]

.buildkite changes LGTM

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: fa73a4d

Metrics [docs]

Unknown metric groups

ESLint disabled in files

id	before	after	diff
observability	6	5	-1
synthetics	6	7	+1
ux	2	3	+1
total			+1

ESLint disabled line counts

id	before	after	diff
observability	50	45	-5
securitySolution	433	436	+3
synthetics	104	107	+3
ux	9	12	+3
total			+4

Total ESLint disabled count

id	before	after	diff
observability	56	50	-6
securitySolution	513	516	+3
synthetics	110	114	+4
ux	11	15	+4
total			+5

History

• 💔 Build #116396 failed 933d409
• 💔 Build #116384 failed 37d78eb761203460169657bda2f66d2ad9489476

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @CoenWarmer