Fix incorrectly nested dtx.

https://tex.stackexchange.com/questions/550540/lgrind-dtx-no-longer-compiles-as-of-tex-live-2020-potential-problem-with-new-la

Index: lgrind.dtx
--- lgrind.dtx.orig
+++ lgrind.dtx
@@ -30,6 +30,7 @@
 \documentclass{ltxdoc}
 \CodelineIndex
 \RecordChanges
+\begin{document}
 \DocInput{lgrind.dtx}
 \end{document}
 %</driver>
@@ -40,7 +41,6 @@
 % \frenchspacing
 % 
 % \GetFileInfo{lgrind.dtx}
-% \begin{document}
 % \title{The \LG{} package\thanks{This file
 %         has version number \fileversion, last
 %         revised \filedate.}}
@@ -537,7 +537,7 @@
 % The meta-symbols and their meanings are:
 % \begin{description}
 % \item[\$] The end of a line
-% \item[\^] The beginning of a line
+% \item[\^{}] The beginning of a line
 % \item[$\backslash$d] A delimiter (space, tab, newline, start of line)
 % \item[$\backslash$a] Matches any string of symbols (like `.*' in lex)
 % \item[$\backslash$p] Matches any identifier. In a procedure definition