gh-51067: Drop unreachable struct.error handler in no-sig DD scan

The loop bound guarantees each slice is exactly dd_size bytes.

Author: gpshead

Lib/zipfile/__init__.py

@@ -1757,10 +1757,7 @@ def _scan_data_descriptor_no_sig(self, fp, offset, end_offset, zip64, chunk_size
             mv = memoryview(chunk)
             for i in range(len(chunk) - dd_size + 1):
                 dd = mv[i:i + dd_size]
-                try:
-                    crc, compress_size, file_size = struct.unpack(dd_fmt, dd)
-                except struct.error:
-                    continue
+                crc, compress_size, file_size = struct.unpack(dd_fmt, dd)
                 if delta + i != compress_size:
                     continue