MC-39893: Revert composer2 changes in mainline

- revert composer2 changes.
- Remove vcs repo

Author: Rrego6

composer.json

@@ -10,12 +10,6 @@
         "preferred-install": "dist",
         "sort-packages": true
     },
-    "repositories": [
-        {
-            "type": "vcs",
-            "url": "https://github.com/magento-commerce/magento-composer-installer"
-        }
-    ],
     "require": {
         "php": "~7.3.0||~7.4.0",
         "ext-bcmath": "*",
@@ -38,8 +32,8 @@
         "colinmollenhour/cache-backend-redis": "1.11.0",
         "colinmollenhour/credis": "1.11.1",
         "colinmollenhour/php-redis-session-abstract": "~1.4.0",
-        "composer/composer": "^1.9 || ^2.0",
-        "magento/magento-composer-installer": "dev-MC-38910",
+        "composer/composer": "^1.9",
+        "magento/magento-composer-installer": ">=0.1.11",
         "elasticsearch/elasticsearch": "~7.7.0",
         "guzzlehttp/guzzle": "^6.3.3",
         "laminas/laminas-captcha": "^2.7.1",

composer.lock

@@ -23,7 +23,7 @@
         "ext-xsl": "*",
         "lib-libxml": "*",
         "colinmollenhour/php-redis-session-abstract": "~1.4.0",
-        "composer/composer": "^1.9 || ^2.0",
+        "composer/composer": "^1.9",
         "guzzlehttp/guzzle": "^6.3.3",
         "laminas/laminas-code": "~3.4.1",
         "laminas/laminas-crypt": "^2.6.0",