Clarify behaviour of exclude_regexes_capture and exclude_regexes_match

[jay4ay]

Updating description to clarify what these options do based on the logic at

trufflehog/pkg/custom_detectors/custom_detectors.go

Line 141 in 8d144c2

// exclude checks

and based on my testing.

Description:

Explain the purpose of the PR.

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?

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