Fix update_version.sh

update_version.sh was attempting to bump strings in files that no longer exist.

(cherry picked from commit 267c3be)

update_version.sh

@@ -65,9 +65,6 @@ if [[ ! $NEW_VERSION == *~rc* ]]; then
     # Upgrade docs to Ubuntu 16.04 reference current stable version explicitly.
     # Where we're talking about the 0.12 _series_ (the first to support Xenial),
     # the phrase "0.12 series" is used, so this regex is safe to run.
-    sed -i "s@$(echo "${OLD_RELEASE}" | sed 's/\./\\./g')@$NEW_VERSION@g" docs/upgrade/xenial_upgrade_in_place.rst
-    sed -i "s@$(echo "${OLD_RELEASE}" | sed 's/\./\\./g')@$NEW_VERSION@g" docs/upgrade/xenial_prep.rst
-    sed -i "s@$(echo "${OLD_RELEASE}" | sed 's/\./\\./g')@$NEW_VERSION@g" docs/upgrade/xenial_backup_install_restore.rst
 fi
 
 # Update the changelog