docs(tutorial): mention that Protractor might need upgrading

Since Protractor requires specific WebDriver versions and these are only
compatible with specific browser version ranges, it is often necessary
to upgrade Protractor just so that it picks up a more recent WebDriver
version.
Related: angular#16739

Author: gkalpak

docs/content/tutorial/index.ngdoc

@@ -281,6 +281,18 @@ It is good to run the E2E tests whenever you make changes to the HTML views or w
 the application as a whole is executing correctly. It is very common to run E2E tests before pushing
 a new commit of changes to a remote repository.
 
+<div class="alert alert-warning">
+  <p>
+    Each version of Protractor is compatible with specific browser versions. If you are reading this
+    some time in the future, it is possible that the specified Protractor version is no longer
+    compatible with the latest version of Chrome that you are using.
+  </p>
+  <p>
+    If that is the case, you can try upgrading Protractor to newer version. For instructions on how
+    to upgrade dependencies see [Updating dependencies](tutorial/#updating-dependencies).
+  </p>
+</div>
+
 
 ### Updating dependencies