Build/Test Tools: Only enforce PHP extension requirements when running core tests.

This allows other users of the WordPress unit test suite framework to run their own unit tests without needing the GD extension, which should only be a requirement if running core tests.

Follow-up to [49535].

Props jamescollins.
Fixes #50640.

git-svn-id: https://develop.svn.wordpress.org/trunk@49571 602fd350-edb4-49c9-b593-d223f7449a82

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": "fcf040d9233a22165eeffaeb98694436",
+    "content-hash": "463db2b4afb439fb63d93173c0852e27",
     "packages": [],
     "packages-dev": [
         {
@@ -131,20 +131,6 @@
                 "constructor",
                 "instantiate"
             ],
-            "funding": [
-                {
-                    "url": "https://www.doctrine-project.org/sponsorship.html",
-                    "type": "custom"
-                },
-                {
-                    "url": "https://www.patreon.com/phpdoctrine",
-                    "type": "patreon"
-                },
-                {
-                    "url": "https://tidelift.com/funding/github/packagist/doctrine%2Finstantiator",
-                    "type": "tidelift"
-                }
-            ],
             "time": "2020-05-29T17:27:14+00:00"
         },
         {
@@ -1851,8 +1837,6 @@
     "platform": {
         "php": ">=5.6"
     },
-    "platform-dev": {
-        "ext-gd": "*"
-    },
+    "platform-dev": [],
     "plugin-api-version": "1.1.0"
 }