Remove a DCHECK in FlocId::FlocId()

In the patch where the DCHECK was added
(https://chromium-review.googlesource.com/c/chromium/src/+/2595595),
the kFlocIdComputeTimePrefKey is also updated. This has caused a
one-time DCHECK failure for some client when Chrome was updated.

The impact scope is small (i.e.should occur at most once per client and
on M89 Canary only, as the PrefKey was initially introduced in M89),
but should still be fixed.

Bug: 1161160
Change-Id: I0fa226fd902ef732710fbfd0ec1d9a050166922d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625569Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Yao Xiao <yaoxia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843051}

components/federated_learning/floc_id.cc

@@ -122,9 +122,6 @@ FlocId::FlocId(base::Optional<uint64_t> id,
       history_end_time_(history_end_time),
       finch_config_version_(finch_config_version),
       sorting_lsh_version_(sorting_lsh_version),
-      compute_time_(compute_time) {
-  // If the floc is never computed, the id should be invalid.
-  DCHECK(!compute_time.is_null() || !id.has_value());
-}
+      compute_time_(compute_time) {}
 
 }  // namespace federated_learning