updated the llvm 21 and 22 links

Author: Ko496-glitch

src/backend/updating-llvm.md

@@ -1,6 +1,5 @@
 # Updating LLVM
 
-<!-- date-check: March 2026 -->
 Rust supports building against multiple LLVM versions:
 
 * Tip-of-tree for the current LLVM development branch is usually supported within a few days.
@@ -91,7 +90,6 @@ An example PR: [#59089](https://github.com/rust-lang/rust/pull/59089)
 
 ## New LLVM Release Updates
 
-<!-- date-check: March 2026 -->
 
 Unlike bugfixes,
 updating to a new release of LLVM typically requires a lot more work.
@@ -178,6 +176,8 @@ so let's go through each in detail.
    > - [LLVM 18](https://github.com/rust-lang/rust/pull/120055)
    > - [LLVM 19](https://github.com/rust-lang/rust/pull/127513)
    > - [LLVM 20](https://github.com/rust-lang/rust/pull/135763)
+   > - [LLVM 21](https://github.com/rust-lang/rust/pull/143684)
+   > - [LLVM 22](https://github.com/rust-lang/rust/pull/150722)
 
    Note that sometimes it's easiest to land [`llvm-wrapper`] compatibility as a PR
    before actually updating `src/llvm-project`.