Update vscode.md java instructions

Add an extra check step in the "Setting up code completion/reference
finding/etc" section.

Change-Id: I1f76849fcb9179b7f6bc0f5669669cbff98c40cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121454
Commit-Queue: Henry Jian <hzjian@google.com>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753675}

docs/vscode.md

@@ -238,6 +238,10 @@ writing:
     * `third_party/android_protobuf/src/java/src/main/java`
     * `third_party/junit/src/src/main/java`
 
+Also, make sure
+`export ANDROID_HOME=/usr/local/google/home/{your_ldap}/Android/Sdk` is in the
+remote machine's `~/.bashrc`.
+
 Then restart vscode, open a Java file, and wait for a bit.
 
 Debugging tips: