Fix a bogus assert in tt.cpp

Max hash size is 4096 MB, not 1024 MB, see the corresponding
"Hash" UCI parameter in ucioption.cpp

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/tt.cpp

@@ -58,7 +58,7 @@ TranspositionTable::~TranspositionTable() {
 
 void TranspositionTable::set_size(unsigned mbSize) {
 
-  assert(mbSize >= 4 && mbSize <= 1024);
+  assert(mbSize >= 4 && mbSize <= 4096);
 
   unsigned newSize = 1024;