Bug 32975: Error in package.json's definition of css:build vs css:build:prod

Bug 32975: Error in package.json's definition of css:build vs css:build:prod

The "css:build" command runs "gulp css && gulp css --view opac",
processes that build CSS in a development context.

The "css:build:prod" currently runs "gulp build && gulp css --view
opac", which runs the production-oriented command "gulp build" (for the
staff interface), but runs "gulp css --view opac" which is the same
devel-environment command as above.

It should be "gulp build && gulp build --view opac"

To test, apply the patch and run the two commands and check these two
files to confirm the difference:

koha-tmpl/intranet-tmpl/prog/css/staff-global.css
koha-tmpl/opac-tmpl/bootstra/css/opac.css

"yarn css:build" should create unminimized versions of those files.
"yarn css:build:prod" should create minimized versions.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>