Empty string works better than 0

Turns out that setting RAKUDO_ERROR_COLOR to 0 does not work well enough across
all Rakudo versions. This causes the output to be different on some commits,
which may freak out bisectable or even committable if ran across many commits.

Empty string works all the time.

Author: AlexDaniel

Perl6IRCBotable.pm

@@ -38,7 +38,7 @@ use constant BUILDS => abs_path('./builds');
 use constant CONFIG => abs_path('./config.json');
 use constant SOURCE => 'https://github.com/perl6/bisectbot';
 
-$ENV{'RAKUDO_ERROR_COLOR'} = 0;
+$ENV{'RAKUDO_ERROR_COLOR'} = '';
 
 sub timeout {
   return 10;