Making PLFA compatible with agda-2.8.0 and stdlib-2.3.0#1122

wenkokke merged 1 commit intoplfa:devplfa/plfa.github.io:devfrom

JacquesCarette:feature-v2.8-v2.3JacquesCarette/plfa.github.io:feature-v2.8-v2.3Copy head branch name to clipboard