[temp] Add missing ';' to grammar for concept-definition.

Despite being a normative change, this matches the overwhelmingly
obvious intent of the committee.

Fixes #1686

Author: zygoloid

source/templates.tex

@@ -49,7 +49,7 @@
 
 \begin{bnf}
 \nontermdef{concept-definition}\br
-  \terminal{concept} concept-name \terminal{=} constraint-expression
+  \terminal{concept} concept-name \terminal{=} constraint-expression \terminal{;}
 \end{bnf}
 
 \begin{bnf}