[dcl.typedef] Fix: change semicolon to full stop.

A miss-edit in the application of P2996R13.

Author: tkoeppe

source/declarations.tex

@@ -763,7 +763,7 @@
 \grammarterm{typedef-name}.
 The underlying entity of the type alias is
 the type associated with the \grammarterm{identifier}\iref{dcl.decl}
-or \grammarterm{simple-template-id}\iref{temp.pre};
+or \grammarterm{simple-template-id}\iref{temp.pre}.
 \indextext{declaration!typedef@\tcode{typedef} as type}%
 \indextext{equivalence!type}%
 A \grammarterm{typedef-name} does not introduce a new type the way a class