md5: Fixed invalid encoding in open

package_release.py

@@ -12,7 +12,7 @@ import alphaplan_fwr
 
 def md5(fname):
     hash_md5 = hashlib.md5()
-    with open(fname, "rb", encoding="utf-8") as f:
+    with open(fname, "rb", encoding=None) as f:
         for chunk in iter(lambda: f.read(4096), b""):
             hash_md5.update(chunk)
     return hash_md5.hexdigest()