[docs] build.tex: fix formatting of example in build environments section

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@13766 3c298f89-4303-0410-b956-a3cf2f4a3e73

docs/build.tex

@@ -547,7 +547,7 @@ The script \texttt{./scripts/env} is used to manage these environments, it uses
 
 The command 
 \begin{Verbatim}
-  \texttt{./scripts/env help}
+  ./scripts/env help
 \end{Verbatim}
 produces a short help text with a list of commands.