Mismatched CodePipeline CloudWatch fields

Hi all, thanks for your support on this library. I was recently trying to replace our homemade structs for CodePipeline events with the ones defined in this package but I'm running into the following errors unmarshalling the `version` fields in `CodePipelineEventDetail` and `CodePipelineEventDetail`:

```Go
json: cannot unmarshal number 2.0 into Go struct field CodePipelineEventDetail.detail.version of type int64: errorString null

json: cannot unmarshal string into Go struct field CodePipelineEventDetailType.detail.type.version of type int64: errorString null
```

The unmarshalling works when `CodePipelineEventDetail.detail.version` is a `float64` and `CodePipelineEventDetailType.detail.type.version` is a string (using our own structs). Would y'all mind taking another look at the types for the two `versions` fields?

Based on the comments for each of them, it sounds like there's some mismatch in the schema/documentation:
https://github.com/aws/aws-lambda-go/blob/96ab249f3eb7644ebc3bb7a190d268184fdd9f4e/events/codepipeline_cloudwatch.go#L82-L83

https://github.com/aws/aws-lambda-go/blob/96ab249f3eb7644ebc3bb7a190d268184fdd9f4e/events/codepipeline_cloudwatch.go#L105-L106

Thanks!

Commencez dans events/codepipeline_cloudwatch.go aux lignes référencées pour les champs version de CodePipelineEventDetail et CodePipelineEventDetailType. Comparez ces déclarations avec les erreurs de JSON unmarshalling signalées et les commentaires, puis confirmez que des valeurs numériques et des chaînes représentatives de version se décodent correctement avec les types corrigés.

Rédigé par le modèle d'indexation à partir du texte de l'issue.