Docs: Give precision on where iOS Chrome is located in the codebase

Change-Id: I34c964a0f7eddc336ca101dbfc64176cdb2f9d15
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1805638Reviewed-by: Darin Fisher <darin@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697113}

chrome/README.md

@@ -11,5 +11,6 @@ Specific products include:
 - Chrome mobile browser for Android
 - Chrome OS system UI
 
-See //ios for the Chrome mobile browser for iOS, and note that code that is
-shared between //chrome and //ios is typically factored out into //components.
+See //ios/chrome for the Chrome mobile browser for iOS, and note that code that
+is shared between //chrome and //ios/chrome is typically factored out into
+//components.