clarifications for Vanadium build instructions

static/build.html

@@ -206,10 +206,12 @@ cd ../..</pre>
 
             <p>You can obtain the proper configuration from the
             <a href="https://github.com/GrapheneOS/Vanadium">
-            GrapheneOS Vanadium repository</a> in <code>args.gn</code> the correct version.</p>
+            GrapheneOS Vanadium repository</a> in <code>args.gn</code> including the correct
+            version.</p>
 
             <pre>git clone https://github.com/GrapheneOS/Vanadium.git
-cd Vanadium</pre>
+cd Vanadium
+git checkout $CORRECT_BRANCH_OR_TAG</pre>
 
             <p>Fetch the Chromium sources:</p>