fix(aws): Remove none extracted value by regex

[ViBiOh]

What does this PR do?

Fix an issue when the multiline regex extract None.

Motivation

This None value lead to an error further in the logs process.

Testing Guidelines

I've set up a lambda with the DD_MULTILINE_LOG_REGEX_PATTERN: (Build:\s)|(Process:\s)|(Timestamp) and send some tricky formatted log to reproduce and fix.

Additional Notes

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
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