removed unread assignment in sed.c

clang scan-build flags up this line as being unread, so clearing from code.

toys/posix/sed.c

@@ -705,7 +705,7 @@ static char *unescape_delimited_string(char **pstr, char *delim, int regex)
 {
  char *to, *from, mode = 0, d;
 
- to = from = *pstr;
+ from = *pstr;
  if (!delim || !*delim) {
  if (!(d = *(from++))) return 0;
  if (d == '\\') d = *(from++);