[Composer] Enforce minimum PHP version during composer update

- Downgrade symfony/yaml to version v3.4.42 to satisfy the enforced minimum PHP version

composer.json

@@ -53,6 +53,9 @@
         }
     },
     "config": {
+        "platform": {
+            "php": "7.1.0"
+        },
         "process-timeout" : 0,
         "autoloader-suffix": "FriendicaDirectory",
 		"optimize-autoloader": true,

composer.lock

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "4ec1d35a2434e8cd6887500404ad427b",
+    "content-hash": "f55a155c5624552ef683137190a85ac3",
     "packages": [
         {
             "name": "asika/simple-console",
@@ -3542,20 +3542,20 @@
         },
         {
             "name": "symfony/yaml",
-            "version": "v4.2.4",
+            "version": "v3.4.42",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/yaml.git",
-                "reference": "761fa560a937fd7686e5274ff89dcfa87a5047df"
+                "reference": "7233ac2bfdde24d672f5305f2b3f6b5d741ef8eb"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/yaml/zipball/761fa560a937fd7686e5274ff89dcfa87a5047df",
-                "reference": "761fa560a937fd7686e5274ff89dcfa87a5047df",
+                "url": "https://api.github.com/repos/symfony/yaml/zipball/7233ac2bfdde24d672f5305f2b3f6b5d741ef8eb",
+                "reference": "7233ac2bfdde24d672f5305f2b3f6b5d741ef8eb",
                 "shasum": ""
             },
             "require": {
-                "php": "^7.1.3",
+                "php": "^5.5.9|>=7.0.8",
                 "symfony/polyfill-ctype": "~1.8"
             },
             "conflict": {
@@ -3570,7 +3570,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "4.2-dev"
+                    "dev-master": "3.4-dev"
                 }
             },
             "autoload": {
@@ -3597,7 +3597,7 @@
             ],
             "description": "Symfony Yaml Component",
             "homepage": "https://symfony.com",
-            "time": "2019-02-23T15:17:42+00:00"
+            "time": "2020-05-11T07:51:54+00:00"
         },
         {
             "name": "vimeo/psalm",
@@ -3830,5 +3830,8 @@
         "ext-gd": "*",
         "ext-json": "*"
     },
-    "platform-dev": []
+    "platform-dev": [],
+    "platform-overrides": {
+        "php": "7.1.0"
+    }
 }