TT#71952 tt2-process: Remove unnecessary asserts

These file arguments are now computed internally, so the pairs should
always be present.

Change-Id: I26f13be3aaf6cc0e935be8cefe916947cd93a965

helper/tt2-process

@@ -327,9 +327,6 @@ sub process {
         my $input = $file->{input};
         my $output = $file->{output};
 
-        error('Missing input file') unless defined $input;
-        error("Missing output file for $input") unless defined $output;
-
         my $pid = fork;
         if (not defined $pid) {
             error("Cannot fork child process to process $input: $!");