Update dreamfactory/df-system requirement from ~0.4 to ~0.5

Updates the requirements on [dreamfactory/df-system](https://github.com/dreamfactorysoftware/df-system) to permit the latest version.
- [Release notes](https://github.com/dreamfactorysoftware/df-system/releases)
- [Changelog](https://github.com/dreamfactorysoftware/df-system/blob/master/CHANGELOG.md)
- [Commits](dreamfactorysoftware/df-system@0.4.0...0.5.0)

---
updated-dependencies:
- dependency-name: dreamfactory/df-system
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -30,7 +30,7 @@
   "prefer-stable": true,
   "require":     {
     "dreamfactory/df-core":   "~0.24",
-    "dreamfactory/df-system": "~0.4"
+    "dreamfactory/df-system": "~0.5"
   },
   "autoload":    {
     "psr-4": {