[defs] Update introduction to match ISO Directives (#5096)

Reference: https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor218

Author: JohelEGP

source/intro.tex

@@ -118,12 +118,12 @@
 and the following apply.
 
 \pnum
-ISO and IEC maintain terminological databases
+ISO and IEC maintain terminology databases
 for use in standardization
 at the following addresses:
 \begin{itemize}
 \item ISO Online browsing platform: available at \url{https://www.iso.org/obp}
-\item IEC Electropedia: available at \url{http://www.electropedia.org/}
+\item IEC Electropedia: available at \url{http://www.electropedia.org}
 \end{itemize}
 
 \pnum