[panw_cortex_xdr] Fix rate limit

[marc-gr]

What does this PR do?

Adds rate limit configuration. Previously was not taken into account and caused issues for some users.

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.

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Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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• Start Time: 2022-07-01T09:20:27.913+0000

• Duration: 15 min 50 sec

Test stats 🧪

Test	Results
Failed	0
Passed	6
Skipped	0
Total	6

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 3.472
Classes	100.0% (1/1)	💚 3.472
Methods	100.0% (14/14)	💚 10.635
Lines	89.655% (390/435)	👎 -1.288
Conditionals	100.0% (0/0)	💚

[djptek]

Fix reported stable & code matches so LGTM