message: docs: fix link in external dependency documentation
diff: @@ -25,8 +25,8 @@ This is the preferred style of adding dependencies that use CMake for their buil
  1. Define a the source Bazel repository in [`bazel/repositories.bzl`](repositories.bzl), in the
  `envoy_dependencies()` function.
  -2. Add a `cmake_external` rule to [`bazel/foreign_cc/BUILD`](bazel/foreign_cc/BUILD). This will
  - reference the source repository in step 1.
  +2. Add a `cmake_external` rule to [`bazel/foreign_cc/BUILD`](foreign_cc/BUILD). This will reference
  + the source repository in step 1.
  3. Reference your new external dependency in some `envoy_cc_library` via the name bound in step 1
  `external_deps` attribute.
  4. `bazel test //test/...`
  