Update phpspec/prophecy requirement from ^1.8 to ^1.10

Updates the requirements on [phpspec/prophecy](https://github.com/phpspec/prophecy) to permit the latest version.
- [Release notes](https://github.com/phpspec/prophecy/releases)
- [Changelog](https://github.com/phpspec/prophecy/blob/master/CHANGES.md)
- [Commits](phpspec/prophecy@1.8.0...v1.10.3)

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

composer.json

@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^7.5",
-        "phpspec/prophecy": "^1.8",
+        "phpspec/prophecy": "^1.10",
         "phpstan/phpstan": "^0.11.5 || ^0.12.0",
         "squizlabs/php_codesniffer": "^3.4.2"
     },