[AWS::BedrockAgentCore::GatewayTarget] - [Docs] - OAuthCredentialProvider CustomParameters with wrong description

### Name of the resource

Other

### Resource name

AWS::BedrockAgentCore::GatewayTarget

### Reference Link

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

### Details

Currently states

> CustomParameters

The OAuth credential provider.

We are on the OAuthCredentialProvider page. The CustomParameters are not the provider itself.
The property needs a better description.

Open the linked AWS CloudFormation reference page for AWS::BedrockAgentCore::GatewayTarget and inspect the OAuthCredentialProvider CustomParameters property description. Update the wording so it describes CustomParameters rather than the OAuth credential provider itself; the issue is done when the property description is accurate and scoped to that field.

Written by the indexing model from the issue text.