swift15: release the numpy view before closing the PLE audit mmap

scripts/verify-swift15-ple.py

@@ -48,10 +48,10 @@ for fname, keys in sorted(shards.items()):
         for k in keys:
             meta = header[k]
             off, end = meta["data_offsets"]
-            assert meta["dtype"] == "BF16", f"{k}: dtype {meta['dtype']}"
             a = np.frombuffer(mm, dtype=np.uint16, count=(end - off) // 2,
                               offset=base + off)
             m = int((a & 0x7FFF).max())
+            del a
             if m > gmax:
                 gmax = m
                 gfile = k