Update version to 14.9.0-rc.1 in Directory.Build.props

Updated the project version from 14.9.0-beta.2 to 14.9.0-rc.1 in the
Directory.Build.props file. This change marks the transition from a
beta release to a release candidate, indicating increased stability
and feature completeness as we approach the final release.

src/Directory.Build.props

@@ -5,6 +5,6 @@
     <Copyright>(C) 2024 edi.wang@outlook.com</Copyright>
     <AssemblyVersion>14.9.0.0</AssemblyVersion>
     <FileVersion>14.9.0.0</FileVersion>
-    <Version>14.9.0-beta.2</Version>
+    <Version>14.9.0-rc.1</Version>
   </PropertyGroup>
 </Project>