ReverseSort bug, exposed but not caused by PHP8 (#1660)

Some tests of ReferenceHelper functions columnReverseSort and
cellReverseSort which passed with PHP7 fail with PHP8.
Both functions use the following construction:
  return 1 - strcasecmp(whatever);
The "1" seems very mysterious. I believe that the correct code should be:
  return -strcasecmp(whatever);
It appears in particular that PHP7 strcasecmp was never returning a
value of 1 for the tests in question, but PHP8 strcasecmp does so.
With the corrected code, the tests pass in both PHP7 and PHP8.

Author: oleibman

src/PhpSpreadsheet/ReferenceHelper.php

@@ -69,7 +69,7 @@ public static function columnSort($a, $b)
      */
     public static function columnReverseSort($a, $b)
     {
-        return 1 - strcasecmp(strlen($a) . $a, strlen($b) . $b);
+        return -strcasecmp(strlen($a) . $a, strlen($b) . $b);
     }
 
     /**
@@ -108,7 +108,7 @@ public static function cellReverseSort($a, $b)
         [$bc, $br] = sscanf($b, '%[A-Z]%d');
 
         if ($ar === $br) {
-            return 1 - strcasecmp(strlen($ac) . $ac, strlen($bc) . $bc);
+            return -strcasecmp(strlen($ac) . $ac, strlen($bc) . $bc);
         }
 
         return ($ar < $br) ? 1 : -1;