Update CHANGELOG_PENDING.md to reflect changes to web identity role provider
### SDK Features
### SDK Enhancements
-* `aws/credentials`: `PolicyArns` can now be passed in to `stscreds.AssumeRoleProvider` in the same way as `sts.AssumeRoleInput`.
+* `aws/credentials`: `PolicyArns` can now be passed in to `stscreds.AssumeRoleProvider` and `stscreds.WebIdentityRoleProvider` in the same way as `sts.AssumeRoleInput`.
### SDK Bugs
