[IAM]: fix opentelekomcloud_identity_user_v3 attribute output

[artem-lifshits]

Summary of the Pull Request

Fix domain_id attribute output for opentelekomcloud_identity_user_v3.

PR Checklist

• Refers to: 1.35.5 removes domain_id from opentelekomcloud_identity_user_v3 #2281
• Tests passed.
• Documentation updated.
• Schema updated.
• Release notes added.

Acceptance Steps Performed

=== RUN   TestAccIdentityV3User_basic
--- PASS: TestAccIdentityV3User_basic (43.67s)
=== RUN   TestAccIdentityV3User_importBasic
--- PASS: TestAccIdentityV3User_importBasic (31.44s)
=== RUN   TestAccCheckIAMV3EmailValidation
--- PASS: TestAccCheckIAMV3EmailValidation (4.84s)
=== RUN   TestAccCheckIAMV3SendEmailValidation
--- PASS: TestAccCheckIAMV3SendEmailValidation (3.70s)
PASS

Process finished with the exit code 0

[otc-zuul]

Build succeeded.
https://zuul.otc-service.com/t/eco/buildset/8af5770a490c471b86e0afcc94b9b9d3

✔️ build-otc-releasenotes SUCCESS in 4m 43s
✔️ otc-golangci-lint SUCCESS in 3m 11s
✔️ golang-make-test SUCCESS in 4m 25s
✔️ golang-make-vet SUCCESS in 3m 37s
✔️ tflint SUCCESS in 2m 51s
✔️ goreleaser-build SUCCESS in 8m 03s