.circleci: rename job from build to doc-build
.circleci: rename job from build to doc-build

kYc0o/RIOT,kYc0o/RIOT,OTAkeys/RIOT,jasonatran/RIOT,OTAkeys/RIOT,ant9000/RIOT,authmillenon/RIOT,miri64/RIOT,kYc0o/RIOT,ant9000/RIOT,authmillenon/RIOT,OlegHahm/RIOT,miri64/RIOT,ant9000/RIOT,miri64/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,OTAkeys/RIOT,jasonatran/RIOT,kYc0o/RIOT,authmillenon/RIOT,miri64/RIOT,ant9000/RIOT,ant9000/RIOT,miri64/RIOT,kaspar030/RIOT,jasonatran/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,jasonatran/RIOT,OlegHahm/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,jasonatran/RIOT,RIOT-OS/RIOT