Remove stale Unity mention from OpenCvSharp4 status row in README

Unity is explicitly unsupported (see the note further down), so listing it as a maintenance target was misleading.

Author: shimat

README.md

@@ -11,7 +11,7 @@ OpenCvSharp is published in two parallel package families:
 | Family | OpenCV | .NET targets | Status |
 |---|---|---|---|
 | **OpenCvSharp5** | 5.0.x | .NET 8+ | Active development — recommended for new projects |
-| **OpenCvSharp4** | 4.13.0 | .NET Framework 4.6.1+, .NET Standard 2.0/2.1, .NET 8+ | Maintenance — for .NET Framework, Unity, or older runtimes |
+| **OpenCvSharp4** | 4.13.0 | .NET Framework 4.6.1+, .NET Standard 2.0/2.1, .NET 8+ | Maintenance — for .NET Framework or older runtimes |
 
 Both families share the same package layout: every `OpenCvSharp5.*` package has an `OpenCvSharp4.*` counterpart. The examples below use **OpenCvSharp5**; replace `5` with `4` for the OpenCvSharp4 family.