Fix runWithClient link in README (#1184)

Use `[]` to treat the content as a link reference label instead of `()`
to treat it as a URL.

pkgs/http/CHANGELOG.md

@@ -1,3 +1,5 @@
+## 1.2.2-wip
+
 ## 1.2.1
 
 * Require Dart `^3.3`

pkgs/http/README.md

@@ -254,7 +254,7 @@ In Flutter, you can use a one of many
 
 If you depend on code that uses top-level functions (e.g. `http.post`) or
 calls the [`Client()`][clientconstructor] constructor, then you can use
-[`runWithClient`](runwithclient) to ensure that the correct
+[`runWithClient`][runwithclient] to ensure that the correct
 `Client` is used. When an [Isolate][isolate] is spawned, it does not inherit
 any variables from the calling Zone, so `runWithClient` needs to be used in
 each Isolate that uses `package:http`.

pkgs/http/pubspec.yaml

@@ -1,5 +1,5 @@
 name: http
-version: 1.2.1
+version: 1.2.2-wip
 description: A composable, multi-platform, Future-based API for HTTP requests.
 repository: https://github.com/dart-lang/http/tree/master/pkgs/http