doc: fix link to Swift gazelle plugin (bazel-contrib#1708)

README.rst

@@ -36,7 +36,7 @@ Gazelle build file generator
 .. _stackb/rules_proto: https://github.com/stackb/rules_proto
 .. _Open a PR: https://github.com/bazelbuild/bazel-gazelle/edit/master/README.rst
 .. _Bazel Slack: https://slack.bazel.build
-.. _swift_bazel: https://github.com/cgrindel/swift_bazel
+.. _rules_swift_package_manager: https://github.com/cgrindel/rules_swift_package_manager
 .. _gazelle_rust: https://github.com/Calsign/gazelle_rust
 .. _rules_rust: https://github.com/bazelbuild/rules_rust
 
@@ -139,7 +139,9 @@ Gazelle can generate Bazel BUILD files for many languages:
 
 * Swift
 
-  `swift_bazel`_ has an extension for generating ``swift_library``, ``swift_binary``, and ``swift_test`` rules. It also includes facilities for resolving, downloading and building external Swift packages for a Bazel workspace.
+  `rules_swift_package_manager`_ has an extension for generating ``swift_library``, ``swift_binary``, and 
+  ``swift_test`` rules. It also includes facilities for resolving, downloading and building external Swift 
+  packages for a Bazel workspace.
 
 If you know of an extension which could be linked here, please `open a PR`_!