Remove deprecated flag from devsite staging script

The parallelize_build flag was removed in cr/400289847. Apparently it has been nonfunctional for a long time and parallelized builds are a default now.

Change-Id: If6def047f7f09e21544f0d9f9f88e8f86d7dced5
diff --git a/development/referenceDocs/stageReferenceDocsWithDackka.sh b/development/referenceDocs/stageReferenceDocsWithDackka.sh
index 8c52bde..19a0d3a8 100755
--- a/development/referenceDocs/stageReferenceDocsWithDackka.sh
+++ b/development/referenceDocs/stageReferenceDocsWithDackka.sh
@@ -275,7 +275,6 @@
 
 # Construct the devsite command and parameters
 devsiteCmd="/google/data/ro/projects/devsite/devsite2 stage"
-devsiteCmd+=" --parallelize_build"
 devsiteCmd+=" --use_large_thread_pools"
 devsiteCmd+=" --upload_safety_check_mode=ignore"