Update php platform version in lock file.

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": "05f17d2c4bef8cc69cf5dc495f390768",
+    "content-hash": "a45d4d824b4556562b32db31f7ef6bd0",
     "packages": [
         {
             "name": "container-interop/container-interop",
@@ -676,7 +676,10 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": ">=5.3.0"
+        "php": ">=7.1"
     },
-    "platform-dev": []
+    "platform-dev": [],
+    "platform-overrides": {
+        "php": "7.1"
+    }
 }