[Enhancement] Adding GCS and ABS to allowed inputs in filebeat spec

[P1llus]

What does this PR do?

Filebeat have two newer inputs that have yet to be added to integration packages. To be able to add these we need to first update the filebeat spec file so they are allowed to run.

Why is it important?

Change is needed to run these new inputs in elastic-agent, and is currently a blocker for us to use them in integration packages.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool

Related issues

• Relates [GCS] Adding new integration for Custom GCS Input integrations#4692
• Relates [Azure Blob Storage] Adding integration for Custom Azure Blob Storage Input integrations#4693

[mergify]

This pull request does not have a backport label. Could you fix it @P1llus? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[P1llus]

I believe the changelog was only for customer facing changes? Is any other changes required for this to be approved?

This is targeting 8.6.1 and newer.

[elasticmachine]

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• Start Time: 2023-01-23T13:48:25.724+0000

• Duration: 19 min 25 sec

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Test	Results
Failed	0
Passed	4825
Skipped	13
Total	4838

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	98.305% (58/59)	👍
Files	69.268% (142/205)	👍
Classes	69.231% (270/390)	👍
Methods	54.047% (828/1532)	👍
Lines	39.237% (9003/22945)	👎 -0.022
Conditionals	100.0% (0/0)	💚