Update ios-app.md to load git_repository
Closes
@@ -100,6 +100,7 @@ repository. To enable this, add the following [`git_repository`](../be/workspace
rules to your `WORKSPACE` file:
```
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
git_repository(
name = "build_bazel_rules_apple",
remote = "https://github.com/bazelbuild/rules_apple.git",
