In `AssumeRoleWithWebIdentity` requests, the RoleArn form paramter is
designated to specify the role to be assumed. It is crucial to note that
the correct key is RoleArn, not RoleARN.
When I used the "RoleARN" form key instead of "RoleArn," I encountered
an error similar to the following:
```xml
<ErrorResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/"><Error><Type></Type><Code>InvalidParameterValue</Code><Message>Role arn:minio:iam:::role/dummy-internal does not exist</Message></Error><RequestId>XXX</RequestId></ErrorResponse>
```
Despite this, certain documentation erroneously employs RoleARN. To
rectify this inconsistency, I have replaced the instances of RoleARN
with the correct RoleArn. However, for other documents that use RoleARN
without specifying the form parameter, no modifications have been made.
Ref:
ba245c6c46/cmd/sts-handlers.go (L50C2-L50C12)
