chore: remove support for Composer v1

Author: shulard

.github/workflows/continuous-integration.yml

@@ -14,7 +14,7 @@ jobs:
       matrix:
         operating-system: [ubuntu-latest, windows-latest, macOS-latest]
         php-versions: ['7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
-        composer-versions: ['composer:v1', 'composer:v2']
+        composer-versions: ['composer:v2']
         dependencies: ["lowest", "highest"]
 
     steps: