[AWS] Fix Billing Dashboard

[legoguy1000]

What does this PR do?

Fixes Billing Dashboard. Replaced incorrect field with proper one.

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

• Closes AWS billing overview dashboard is broken #4082

Screenshots

[elasticmachine]

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Build stats

• Start Time: 2022-08-30T07:46:59.835+0000

• Duration: 39 min 50 sec

Test stats 🧪

Test	Results
Failed	0
Passed	162
Skipped	2
Total	164

🤖 GitHub comments

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[tommyers-elastic]

thank you!!

[flash1293]

dashboard changes lgtm

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (13/13)	💚
Files	92.857% (13/14)	👎 -4.247
Classes	92.857% (13/14)	👎 -4.247
Methods	84.232% (203/241)	👎 -4.98
Lines	95.697% (5204/5438)	👍 3.945
Conditionals	100.0% (0/0)	💚