Remove VSCode rust-analyzer setting that no longer exists (rust-lang#1096)

Co-authored-by: Adrian Palacios <[email protected]>

Author: 2 people

docs/src/rustc-hacks.md

@@ -14,7 +14,6 @@ In order to get these features working for `rustc` crates, you can do the follow
 
 Add the following to the `rust-analyzer` extension settings in `settings.json`:
 ```json
-    "rust-analyzer.updates.channel": "nightly",
     "rust-analyzer.rustcSource": "discover",
     "rust-analyzer.workspace.symbol.search.scope": "workspace_and_dependencies",
 ```