meta:git-hooks:commit-msg: Fix typo

I have no idea how I have not noticed this yet, as apparently every time
I wrote a commit message that contains a body and not just a subject I
got an error message complaining that the first word does not exist as a
command. (With the exception of when it actually is, but then executing
arbitrary code)

meta/git/hooks/commit-msg

@@ -45,7 +45,7 @@ done
 BKP_IFS="$IFS"
 IFS='
 '
-for line in $($body); do
+for line in $body; do
 	[[ ${#line} -le 72 ]] || die "Body lines too long. (<= 72)\n"
 done
 IFS="$BKP_IFS"