Revert "MMAP: Build ADT floor just like WMO floor below liquid (#27503)" (#28392)

This reverts commit 8a779268b6.

(cherry picked from commit b69870630d)

src/tools/mmaps_generator/TerrainBuilder.cpp

@@ -448,6 +448,10 @@ namespace MMAP
                             minTLevel = h;
                     }
 
+                    // terrain under the liquid?
+                    if (minLLevel > maxTLevel)
+                        useTerrain = false;
+
                     //liquid under the terrain?
                     if (minTLevel > maxLLevel)
                         useLiquid = false;