fix typo in coeffects.md;
fix typo in coeffects.md;

Day8/re-frame,martinklepsch/re-frame,chpill/re-frankenstein,Day8/re-frame,daiyi/re-frame,chpill/re-frankenstein,Day8/re-frame,richardharrington/re-frame,martinklepsch/re-frame,richardharrington/re-frame,daiyi/re-frame,chpill/re-frankenstein,daiyi/re-frame,richardharrington/re-frame,martinklepsch/re-frame