Move ios documentation from //docs to //docs/ios.

[email protected]
BUG=none

Review-Url: https://codereview.chromium.org/2731293003
Cr-Commit-Position: refs/heads/master@{#454972}
diff --git a/docs/get_the_code.md b/docs/get_the_code.md
index cc834b56..0d637d4 100644
--- a/docs/get_the_code.md
+++ b/docs/get_the_code.md
@@ -12,7 +12,7 @@
 * [Android](android_build_instructions.md)
 * [Cast](old_cast_build_instructions.md)
 * [Chrome OS](old_chromeos_build_instructions.md)
-* [iOS](ios_build_instructions.md)
+* [iOS](ios/build_instructions.md)
 * [Linux](linux_build_instructions.md)
 * [Mac](mac_build_instructions.md)
 * [Windows](windows_build_instructions.md)