build: remove unused development dependency seedrandom

The `seedrandom` dependency is not currently used within the package or project.
As a result, it has been removed to prevent unneeded packages from being installed during development.

Author: clydin

packages/angular_devkit/core/package.json

@@ -22,8 +22,5 @@
     "chokidar": {
       "optional": true
     }
-  },
-  "devDependencies": {
-    "seedrandom": "^3.0.0"
   }
 }

yarn.lock

@@ -10075,11 +10075,6 @@ schema-utils@^4.0.0:
     ajv-formats "^2.1.1"
     ajv-keywords "^5.0.0"
 
-seedrandom@^3.0.0:
-  version "3.0.5"
-  resolved "https://registry.yarnpkg.com/seedrandom/-/seedrandom-3.0.5.tgz#54edc85c95222525b0c7a6f6b3543d8e0b3aa0a7"
-  integrity sha512-8OwmbklUNzwezjGInmZ+2clQmExQPvomqjL7LFqOYqtmuxRgQYqOD3mHaU+MvZn5FLUeVxVfQjwLZW/n/JFuqg==
-
 select-hose@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/select-hose/-/select-hose-2.0.0.tgz#625d8658f865af43ec962bfc376a37359a4994ca"