update comment in attestation_flow.h

The comment used to points readers to a deprecated cryptohome client
API; corrected it to the right one.

BUG=b:158955123
TEST=build ok.
Change-Id: I31e99fb8c0b466e04584911ada227af06eaca96f

Change-Id: I5e7657d7f02abb7398b639206c0830792de857b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2430685Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Leo Lai <cylai@google.com>
Cr-Commit-Position: refs/heads/master@{#811175}

chromeos/attestation/attestation_flow.h

@@ -140,8 +140,8 @@ class COMPONENT_EXPORT(CHROMEOS_ATTESTATION) AttestationFlow {
   void WaitForAttestationPrepared(base::TimeTicks end_time,
                                   base::OnceCallback<void(bool)> callback);
 
-  // Handles the result of a call to TpmAttestationIsPrepared. Starts enrollment
-  // on success and retries after |retry_delay_| if not.
+  // Handles the result of a call to GetEnrollmentPreparations. Starts
+  // enrollment on success and retries after |retry_delay_| if not.
   //
   // Parameters
   //   end_time - Time after which preparation should time out.