README: fix ghcup link for channels

Author: ulysses4ever

README.md

@@ -200,7 +200,7 @@ jobs:
 | `stack-setup-ghc`       | If set, `enable-stack` must be set. Runs stack setup to install the specified GHC. (Note: setting this does _not_ imply `stack-no-global`.) | "boolean" | false/unset |
 | `disable-matcher`       | If set, disables match messages from GHC as GitHub CI annotations.                                                                          | "boolean" | false/unset |
 | `cabal-update`          | If set to `false`, skip `cabal update` step.                                                                                                | `boolean` | `true`      |
-| `ghcup-release-channel` | If set, add a [release channel](https://www.haskell.org/ghcup/guide/#pre-release-channels) to ghcup.                                        | `URL`     | none        |
+| `ghcup-release-channel` | If set, add a [release channel](https://www.haskell.org/ghcup/guide/#metadata) to ghcup.                                        | `URL`     | none        |
 
 Note: "boolean" types are set/unset, not true/false.
 That is, setting any "boolean" to a value other than the empty string (`""`) will be considered true/set.