[AWS::BedrockAgentCore::GatewayTarget] - [Docs] - CredentialProviderConfigurations with wrong description

### Name of the resource

Other

### Resource name

AWS::BedrockAgentCore::GatewayTarget

### Reference Link

https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-bedrockagentcore-gatewaytarget.html

### Details

Currently states

> The OAuth credential provider configuration.

But there are GATEWAY_IAM_ROLE and API_KEY authentications too that can be specified here instead. Needs to be generalized.

Open the referenced AWS CloudFormation resource documentation for AWS::BedrockAgentCore::GatewayTarget and locate the CredentialProviderConfigurations description. Generalize the wording so it covers GATEWAY_IAM_ROLE and API_KEY as well as OAuth, then verify the published description no longer implies OAuth is the only option.

Written by the indexing model from the issue text.