Smithy NullAndEmptyHeaders protocol tests will be ignored until they are published by Smithy

[Madrigal]

Acknowledgements

• [X] I have searched (https://github.com/aws/aws-sdk/issues?q=is%3Aissue) for past instances of this issue
• [X] I have verified all of my SDK modules are up-to-date (you can perform a bulk update with go get -u github.com/aws/aws-sdk-go-v2/...)

Describe the bug

Smithy has updated their protocol tests to allow non-nil empty headers in smithy-lang/smithy#2403 However, these updated tests haven't been released as of Smithy 1.51.0.

When we push a fix for the issue, we need to temporarily skip these tests until they are fixed

Regression Issue

• [ ] Select this option if this issue appears to be a regression.

Expected Behavior

All protocol tests should pass ideally, but these are expected to be broken until they are published

Current Behavior

These protocol tests fail, but it's expected until Smithy publishes the new version

Reproduction Steps

make unit

Possible Solution

No response

Additional Information/Context

No response

AWS Go SDK V2 Module Versions Used

n/a

Compiler and Version used

n/a

Operating System and version

n/a