docs: update .NET 11 preview README release info (dotnet#10372)

Author: WeihanLi

release-notes/11.0/preview/README.md

@@ -6,5 +6,6 @@
 
 | Date | Release |
 | ---- | ------- |
-| TBD | [11.0.0 Preview 2](./preview2/README.md) |
+| 2026/04/14 | [11.0.0 Preview 3](./preview3/README.md) |
+| 2026/03/10 | [11.0.0 Preview 2](./preview2/README.md) |
 | 2026/02/10 | [11.0.0 Preview 1](./preview1/README.md) |