Replace a predicate that was always false with a literal (#151)

* Replace a predicate that was always false with a literal

* comment + fix mvcc version

Signed-off-by: Alex Chi <iskyzh@gmail.com>

---------

Signed-off-by: Alex Chi <iskyzh@gmail.com>
Co-authored-by: Alex Chi <iskyzh@gmail.com>

mini-lsm/src/compact/tiered.rs

@@ -90,7 +90,8 @@ impl TieredCompactionController {
                         .take(id + 1)
                         .cloned()
                         .collect::<Vec<_>>(),
-                    bottom_tier_included: id + 1 >= snapshot.levels.len(),
+                    // Size ratio trigger will never include the bottom level
+                    bottom_tier_included: false,
                 });
             }
         }