Drop building internal docs

They are causing the Jenkins release job to fail and no one really cares
about those

Change-Id: I6c4bd7923dd85772c6fd678fafb172b875e27b8a
diff --git a/tools/build/onos-build-docs b/tools/build/onos-build-docs
index 3be4c0a..376a7c2 100755
--- a/tools/build/onos-build-docs
+++ b/tools/build/onos-build-docs
@@ -3,4 +3,4 @@
 # Builds the aggregate ONOS Java API docs.
 # -----------------------------------------------------------------------------
 
-SHLVL=1 bazel build //docs:external //docs:internal
+SHLVL=1 bazel build //docs:external