[HAProxy] Remove uncessary Timezone default in manifest

[P1llus]

What does this PR do?

Followup on the older PR #6767, the UTC default is unecessary and should have been removed.

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.

[elasticmachine]

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• Start Time: 2023-06-30T15:56:59.782+0000

• Duration: 16 min 18 sec

Test stats 🧪

Test	Results
Failed	0
Passed	40
Skipped	0
Total	40

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 2.178
Classes	100.0% (1/1)	💚 2.178
Methods	90.476% (19/21)	👎 -4.271
Lines	97.297% (180/185)	👍 5.183
Conditionals	100.0% (0/0)	💚

[elasticmachine]

Package haproxy - 1.7.1 containing this change is available at https://epr.elastic.co/search?package=haproxy