Update CI to .NET SDK 5.0.300

Author: GlebChili

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 env:
   GMODNET_VERSION: '0.6.0'
-  DOTNET_SDK_VERSION: '5.0.202'
+  DOTNET_SDK_VERSION: '5.0.300'
 
 jobs:
  linux-build: