Update mockery/mockery requirement from 1.3.0 to 1.3.1

Updates the requirements on [mockery/mockery](https://github.com/mockery/mockery) to permit the latest version.
- [Release notes](https://github.com/mockery/mockery/releases)
- [Changelog](https://github.com/mockery/mockery/blob/master/CHANGELOG.md)
- [Commits](mockery/mockery@1.3.0...1.3.1)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

composer.json

@@ -7,7 +7,7 @@
     "require-dev": {
         "laravel/laravel": "~5.5||~6.0",
         "phpunit/phpunit": "~7.5",
-        "mockery/mockery": "1.3.0"
+        "mockery/mockery": "1.3.1"
     },
     "license": "MIT",
     "authors": [