fix(helm): remove broken hubble-ui backend health probes

[Sébastien Larivière (slariviere)]

Description

What

Removes the hubble.ui.backend.livenessProbe / readinessProbe values
and the associated startupProbe/livenessProbe/readinessProbe templates
for the hubble-ui backend container.

Why

The backend container is a gRPC-only server on port 8090 with no HTTP
endpoints. The probes were configured as httpGet /healthz, which never
works — enabling them causes the container to CrashLoopBackOff.

Upstream cilium hit the same issue (cilium/cilium#43501) and fixed it by
removing the feature outright in cilium/cilium@b6e50b3, since there's no
working HTTP health endpoint to probe. This PR aligns with that upstream
fix.

Checklist

• I have read the contributing documentation.
• I signed and signed-off the commits (git commit -S -s ...). See this documentation on signing commits.
• I have correctly attributed the author(s) of the code.
• I have tested the changes locally.
• I have followed the project's style guidelines.
• I have updated the documentation, if necessary.
• I have added tests, if applicable.

[github-actions]

This PR will be closed in 7 days due to inactivity.

[Sébastien Larivière (slariviere)]

Timothy J. Raymond (@timraymond) Qingchuan Hao (@mainred), is there anything we can do to move this PR forward?

[Quang Nguyen (nddq)]

upstream removed this a while back cilium/cilium@b6e50b3

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[azure-pipelines]

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[Sébastien Larivière (slariviere)]

upstream removed this a while back cilium/cilium@b6e50b3

Quang Nguyen (@nddq) probes removed as upstream