Update YCM part in VSCode docs

Before running git submodule, we need to change dir first.

Bug: None
Change-Id: I99b335a015f8cbbb122fb23f3d08969caf66ecdc
Reviewed-on: https://chromium-review.googlesource.com/647048
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499193}

docs/vscode.md

@@ -81,8 +81,8 @@ To install You-Complete-Me, enter these commands in a terminal:
 
 ```
 $ git clone https://github.com/Valloric/ycmd.git ~/.ycmd
-$ git submodule update --init --recursive
 $ cd ~/.ycmd
+$ git submodule update --init --recursive
 $ ./build.py --clang-completer
 ```
 If it fails with "Your C++ compiler does NOT fully support C++11." but you know
@@ -541,4 +541,4 @@ might want to disable git status autorefresh as well.
 
 ### More
 More tips and tricks can be found
-[here](https://github.com/Microsoft/vscode-tips-and-tricks/blob/master/README.md).
+[here](https://github.com/Microsoft/vscode-tips-and-tricks/blob/master/README.md).