Use CURRENT_RUSTC_VERSION

This does technically set a deadline for this PR
to merge

Author: DJMcNab

compiler/rustc_feature/src/removed.rs

@@ -102,9 +102,9 @@ declare_features! (
     /// Allows deriving traits as per `SmartPointer` specification
     (removed, derive_smart_pointer, "1.84.0", Some(123430), Some("replaced by `CoercePointee`"), 131284),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
-    (removed, doc_auto_cfg, "1.58.0", Some(43781), Some("merged into `doc_cfg`"), 138907),
+    (removed, doc_auto_cfg, "CURRENT_RUSTC_VERSION", Some(43781), Some("merged into `doc_cfg`"), 138907),
     /// Allows `#[doc(cfg_hide(...))]`.
-    (removed, doc_cfg_hide, "1.57.0", Some(43781), Some("merged into `doc_cfg`"), 138907),
+    (removed, doc_cfg_hide, "CURRENT_RUSTC_VERSION", Some(43781), Some("merged into `doc_cfg`"), 138907),
     /// Allows using `#[doc(keyword = "...")]`.
     (removed, doc_keyword, "1.58.0", Some(51315),
      Some("merged into `#![feature(rustdoc_internals)]`"), 90420),