maint: update quoting of "Try `prog --help'" to "Try 'prog --help'"

Automatically adjust both the source (now in only one place)
and all tests that expect the resulting output via this:

git grep -l 'Try.*--help' src/system.h tests \
  | xargs perl -pi -e 's/Try \\?`(\S+ --help)/Try '\''$1/'

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/misc/invalid-opt b/tests/misc/invalid-opt
index 68e61df8e..8eae3c275 100755
--- a/tests/misc/invalid-opt
+++ b/tests/misc/invalid-opt
@@ -65,7 +65,7 @@ foreach my $prog (@built_programs)
     $prog eq '['
       and next;
 
-    my $try = "Try \`$prog --help' for more information.\n";
+    my $try = "Try '$prog --help' for more information.\n";
     my $x = $exit_status{$prog};
     defined $x
       or $x = 1;