unused variable, just remove it. (#2082)

Signed-off-by: Nwater32 <miaochen@mail.ustc.edu.cn>

unused variable, just remove it.

core/src/db/DBImpl.cpp

@@ -1033,7 +1033,6 @@ DBImpl::GetVectorByID(const std::string& collection_id, const IDNumber& vector_i
 
     std::vector<int> file_types{meta::SegmentSchema::FILE_TYPE::RAW, meta::SegmentSchema::FILE_TYPE::TO_INDEX,
                                 meta::SegmentSchema::FILE_TYPE::BACKUP};
-    meta::SegmentsSchema collection_files;
     status = meta_ptr_->FilesByType(collection_id, file_types, files_to_query);
     if (!status.ok()) {
         std::string err_msg = "Failed to get files for GetVectorByID: " + status.message();