Show abbreviations in the substitution plan only once

The substitution plan shows the abbreviations in multiple repetition under 'teachers affected'.

changed the description

assigned to @hansegucker

added part::backend type::bug workflow::confirmed labels

Huh? Is this a regression in 2.0b0?

created merge request !178 (merged) to address this issue

mentioned in merge request !178 (merged)

closed with merge request !178 (merged)

mentioned in commit 2bb8b808

reopened

created merge request !181 (merged) to address this issue

mentioned in merge request !181 (merged)

closed with merge request !181 (merged)