XXS: Update a comment in the safebrowsing.proto file

components/safe_browsing_db/safebrowsing.proto

Index: components/safe_browsing_db/safebrowsing.proto
diff --git a/components/safe_browsing_db/safebrowsing.proto b/components/safe_browsing_db/safebrowsing.proto
index d533892068810f23b78698d4bdc05b207fea4455..c9c24deb953494bc47915a7f508781a1a2b76398 100644
--- a/components/safe_browsing_db/safebrowsing.proto
+++ b/components/safe_browsing_db/safebrowsing.proto
@@ -149,8 +149,8 @@ message FetchThreatListUpdatesResponse {
     // response.
     repeated ThreatEntrySet additions = 5;
 
-    // A set of entries to remove from a local threat type's list. Repeated for
-    // the same reason as above.
+    // A set of entries to remove from a local threat type's list. In practice,
+    // this field is empty or contains exactly one ThreatEntrySet.
     repeated ThreatEntrySet removals = 6;
 
     // The new client state, in encrypted format. Opaque to clients.