bin: fix some --help typos

Reported by František Blahoudek.

* bin/genaut.cc, bin/autcross.cc: Fix help strings.

bin/autcross.cc

@@ -56,7 +56,7 @@
 const char argp_program_doc[] ="\
 Call several tools that process automata and cross-compare their output \
 to detect bugs, or to gather statistics.  The list of automata to use \
-should be supplied on standard input, or using the -f or -F options.\v\
+should be supplied on standard input, or using the -F option.\v\
 Exit status:\n\
   0  everything went fine (timeouts are OK too)\n\
   1  some tools failed to output something we understand, or failed\n\

bin/genaut.cc

@@ -55,10 +55,10 @@ static const argp_option options[] =
       "deterministic co-Büchi automaton has at least 2^N/(2N+1) states.", 0},
     { "l-nba", gen::AUT_L_NBA, "RANGE", 0,
       "A Büchi automaton with 3N+1 states whose complementary Streett "
-      "automaton needs at least n! states.", 0},
+      "automaton needs at least N! states.", 0},
     { "l-dsa", gen::AUT_L_DSA, "RANGE", 0,
       "A deterministic Streett automaton with 4N states with no "
-      "equivalent deterministic Rabin automaton of less than n! states.", 0},
+      "equivalent deterministic Rabin automaton of less than N! states.", 0},
     RANGE_DOC,
   /**************************************************/
     { nullptr, 0, nullptr, 0, "Miscellaneous options:", -1 },