[DTC] Cleanup UserDTCInlineFlowEnabled feature flag

Bug: b:279840937
Change-Id: Idea521244304aca86c7c30ba9848babf87a76dd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4915846
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Hamda Mare <hmare@google.com>
Commit-Queue: Sébastien Lalancette <seblalancette@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1208869}

chrome/browser/BUILD.gn

@@ -6391,8 +6391,6 @@ static_library("browser") {
       "enterprise/connectors/device_trust/attestation/browser/google_keys.h",
       "enterprise/connectors/device_trust/attestation/browser/profile_attester.cc",
       "enterprise/connectors/device_trust/attestation/browser/profile_attester.h",
-      "enterprise/connectors/device_trust/attestation/desktop/desktop_attestation_service.cc",
-      "enterprise/connectors/device_trust/attestation/desktop/desktop_attestation_service.h",
       "enterprise/connectors/device_trust/browser/signing_key_policy_observer.cc",
       "enterprise/connectors/device_trust/browser/signing_key_policy_observer.h",
       "enterprise/connectors/device_trust/signals/decorators/browser/browser_signals_decorator.cc",