remove ubuntu version documentation

A few of the scripts which utilize a version of an Ubuntu container when
making a dependent Docker container also document the default choice in
comments.  This leads to redundant, and sometimes missed, changes
whenever upgrading the underlying Ubuntu distro version.  Strike them
to reduce this maintenance.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Idc64437a6c6b1f07b6d716829b41b9fd58e62cc3
3 files changed