[cloudflare] Fix lookup of invalid key for pagination

[taylor-swanson]

What does this PR do?

• Change lookup of key for array length from 'response' to 'result'

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.

Related issues

• Closes [cloudflare] Lookup of length of last response breaks pagination #4195

[elasticmachine]

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• Start Time: 2022-09-12T21:13:26.040+0000

• Duration: 15 min 47 sec

Test stats 🧪

Test	Results
Failed	0
Passed	94
Skipped	0
Total	94

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (3/3)	💚 2.537
Classes	100.0% (3/3)	💚 2.537
Methods	100.0% (36/36)	💚 9.77
Lines	95.17% (670/704)	👍 4.269
Conditionals	100.0% (0/0)	💚

[elasticmachine]

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

[kgeller]

One question, otherwise LGTM

[taylor-swanson]

/test