doc: fix docs for rustc 1.92+ (delta-io#1470)

## What changes are proposed in this pull request?
Noticed docs didn't build successfully for [0.17.0
release](https://docs.rs/crate/delta_kernel/0.17.0/builds/2652981) since
in rustc 1.92 the `doc_auto_cfg` feature was removed (and TIL docs.rs
builds with nightly). This pr just moves from the `doc_auto_cfg` to
`doc_cfg` (see associated [rust
pr](rust-lang/rust#138907)).

## How was this change tested?
docs only. reproed with `cargo +nightly doc`

Author: zachschuermann

kernel/src/lib.rs

@@ -50,7 +50,7 @@
 //! connectors are asked to provide the context information they require to execute the actual
 //! operation. This is done by invoking methods on the [`StorageHandler`] trait.
 
-#![cfg_attr(all(doc, NIGHTLY_CHANNEL), feature(doc_auto_cfg))]
+#![cfg_attr(all(doc, NIGHTLY_CHANNEL), feature(doc_cfg))]
 #![warn(
     unreachable_pub,
     trivial_numeric_casts,