Remove unused variable.

Test: Builds with -Wunused-variable
Change-Id: Ibe6c28c8dd510303450f8400ba7d721fd5c44fc3
diff --git a/fs_mgr/libsnapshot/scratch_super.cpp b/fs_mgr/libsnapshot/scratch_super.cpp
index 805abf3..93c4bbd 100644
--- a/fs_mgr/libsnapshot/scratch_super.cpp
+++ b/fs_mgr/libsnapshot/scratch_super.cpp
@@ -98,7 +98,6 @@
     }
     const auto& opener = info->GetPartitionOpener();
     std::string slot_suffix = info->GetSlotSuffix();
-    int slot = SlotNumberForSlotSuffix(slot_suffix);
     // Walk both the slots and clean up metadata related to scratch space from
     // both the slots.
     for (auto slot : slots) {