Cherry-pick #22892 to 7.x: [Filebeat][Cisco] Fix umbrella config: add input var

[marc-gr]

Cherry-pick of PR #22892 to 7.x branch. Original message:

What does this PR do?

Adds input var to cisco umbrella config

Why is it important?

Config expects input variable to be either s3 or file but none is provided, breaking the default config.

The error we get is:
Exiting: Error getting config for fileset cisco/umbrella: Error interpreting the template of the input: template: text:1:9: executing "text" at <.input>: map has no entry for key "input"

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.next.asciidoc or CHANGELOG-developer.next.asciidoc.

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

[elasticmachine]

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Build stats

• Build Cause: Pull request #22894 opened

• Start Time: 2020-12-03T14:56:56.006+0000

• Duration: 47 min 52 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1970
Skipped	259
Total	2229

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Test stats 🧪

Test	Results
Failed	0
Passed	1970
Skipped	259
Total	2229