Remove symlinks to BUILD.gn files

driver/BUILD.gn and third_party/BUILD.gn have been moved to the
corresponding submodules and therefore do not need to be symlinked
from the manifest anymore.

Change-Id: I9053b568d49ceed0c6dc1c6ef3418781781221c4
diff --git a/default.xml b/default.xml
index 3937000..08b398b 100644
--- a/default.xml
+++ b/default.xml
@@ -21,10 +21,6 @@
     <linkfile src="src" dest="src" />
     <linkfile src="test" dest="test" />
     <linkfile src="vmlib" dest="vmlib" />
-
-    <!-- TODO: Move these inside the respective folders -->
-    <linkfile src="driver/BUILD.gn" dest="driver/BUILD.gn" />
-    <linkfile src="third_party/BUILD.gn" dest="third_party/BUILD.gn" />
   </project>
 
   <!-- Shallow clones of third-party code. -->