revert istio release from ga to beta

[gsantoro]

What does this PR do?

Revert release of Istio integration from GA back to Beta

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Relates Feature/istio metrics #4253

Screenshots

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Build stats

• Start Time: 2022-11-21T10:08:24.528+0000

• Duration: 16 min 8 sec

Test stats 🧪

Test	Results
Failed	0
Passed	14
Skipped	0
Total	14

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (3/3)	💚 2.941
Classes	100.0% (3/3)	💚 2.941
Methods	90.0% (27/30)	👍 1.091
Lines	97.472% (347/356)	👍 6.499
Conditionals	100.0% (0/0)	💚

[tetianakravchenko]

note: this field is deprecated elastic/package-spec#256