Fix integer conversion loss warnings for size_t to int (#7095)

Author: paulb777

Firestore/core/src/local/leveldb_lru_reference_delegate.cc

@@ -147,7 +147,8 @@ int LevelDbLruReferenceDelegate::RemoveOrphanedDocuments(
 
 int LevelDbLruReferenceDelegate::RemoveTargets(
     ListenSequenceNumber sequence_number, const LiveQueryMap& live_queries) {
-  return db_->target_cache()->RemoveTargets(sequence_number, live_queries);
+  return static_cast<int>(
+      db_->target_cache()->RemoveTargets(sequence_number, live_queries));
 }
 
 bool LevelDbLruReferenceDelegate::IsPinned(const DocumentKey& key) {

Firestore/core/src/local/memory_lru_reference_delegate.cc

@@ -116,8 +116,8 @@ size_t MemoryLruReferenceDelegate::GetSequenceNumberCount() {
 int MemoryLruReferenceDelegate::RemoveTargets(
     model::ListenSequenceNumber sequence_number,
     const LiveQueryMap& live_queries) {
-  return persistence_->target_cache()->RemoveTargets(sequence_number,
-                                                     live_queries);
+  return static_cast<int>(persistence_->target_cache()->RemoveTargets(
+      sequence_number, live_queries));
 }
 
 int MemoryLruReferenceDelegate::RemoveOrphanedDocuments(