feature attribution for retry mode should not include "legacy"

[kuhe]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

in user agent check-features.ts file, the detection of pre-SRA retries should not attribute the retry as "legacy" mode. It should differentiate and set the feature as either (pre-SRA) standard or (pre-SRA) adaptive.

Legacy refers to the retry behavior in AWS SDK JSv2, which does not exist in this SDK.

Regression Issue

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

SDK version number

https://github.com/aws/aws-sdk-js-v3/releases/tag/v3.669.0

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

any

Reproduction Steps

make a request with pre-SRA retries and inspect the user agent feature metadata

Observed Behavior

it contains D for legacy

Expected Behavior

it should contain either F or E for adaptive/standard.

Possible Solution

No response

Additional Information/Context

No response

[kuhe]

SRA retries were released in Dec '22 but don't appear in the changelog, perhaps due to formatting error in the commit message

https://github.com/aws/aws-sdk-js-v3/compare/v3.228.0..v3.229.0