build-unit-test-docker: force refresh container

prettier had a breaking update which causes some of our markdown
files to fail formatting with the new version.  Force a refresh
so that all the CI containers are on the latest version at the
same time (otherwise different CI containers disagree at the proper
formatting).

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ic304f4d6407d0aaf18110f31b27e5783f8eb545a
1 file changed