TT#71952 tt2-process: Add missing parenthesis around sort

This makes sure we sort each array, instead of sorting the second, and
then letting perl merge the first aray with the result of the second
sort, and then sorting them all as a single array.

Change-Id: I7cd22bf479fee79c104627bf652f0ee674117eec
Fixes: commit 011ce33f32

helper/tt2-process

@@ -295,7 +295,7 @@ sub generate_iofiles {
     my @filenames = map { {
         input => $_,
         output => $filenames{$_},
-    } } (sort @filenames_prio, sort @filenames_norm);
+    } } (sort(@filenames_prio), sort(@filenames_norm));
 
     return @filenames;
 }