Comment the DecodeIgnore database opening stuff

heed/src/cookbook.rs

@@ -36,6 +36,8 @@
 //! };
 //!
 //! let rtxn = env.read_txn()?;
+//! // The database names are mixed with the user entries therefore we prefer
+//! // ignoring the values and try to open the databases one by one using the keys.
 //! let unnamed: Database<Str, DecodeIgnore> =
 //! env.open_database(&rtxn, None)?.expect("the unnamed database always exists");
 //!