cisco_asa: remove invalid values from ECS fields

[efd6]

What does this PR do?

This removes invalid values from the event.outcome field.

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

• Relates cisco_ftd: remove invalid values from ECS fields #3344
• Relates Packages using invalid values for fields according to ECS #3016

Screenshots

[elasticmachine]

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

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-05-16T01:10:31.556+0000

• Duration: 16 min 24 sec

Test stats 🧪

Test	Results
Failed	0
Passed	29
Skipped	0
Total	29

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 3.448
Classes	100.0% (1/1)	💚 3.448
Methods	94.444% (17/18)	👍 5.848
Lines	63.155% (1097/1737)	👎 -25.771
Conditionals	100.0% (0/0)	💚