refactor: derive the bus escort from the travel date

tests/Entity/StaffingRuleTest.php

@@ -39,7 +39,6 @@ class StaffingRuleTest extends TestCase
         yield 'split with more levels than guides' => [self::rule(1, beginner: true, advanced: true, split: true), ['split']];
         yield 'split without a level' => [self::rule(2, split: true), ['split']];
         yield 'guiding without a guide' => [self::rule(0, beginner: true, guiding: true), ['guiding']];
-        yield 'bus escort without a guide' => [self::rule(0, beginner: true, busEscort: true), ['busEscort']];
         yield 'courses without guides' => [self::rule(0, beginner: true), []];
     }
 
@@ -49,7 +48,6 @@ class StaffingRuleTest extends TestCase
         bool $advanced = false,
         bool $split = false,
         bool $guiding = false,
-        bool $busEscort = false,
     ): StaffingRule {
         return (new StaffingRule())
             ->setProductCode('DKIMP')
@@ -58,7 +56,6 @@ class StaffingRuleTest extends TestCase
             ->setSkiAdvanced($advanced)
             ->setSplit($split)
             ->setGuiding($guiding)
-            ->setBusEscort($busEscort)
         ;
     }
 }