Bump to LangVersion 14

Author: bradwilson

src/Directory.Build.props

@@ -17,7 +17,7 @@
     <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
     <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
-    <LangVersion>12.0</LangVersion>
+    <LangVersion>14.0</LangVersion>
     <MicrosoftCodeAnalysisVersion Condition=" '$(MicrosoftCodeAnalysisVersion)' == '' ">3.11</MicrosoftCodeAnalysisVersion>
     <MSBuildCopyContentTransitively>false</MSBuildCopyContentTransitively>
     <Nullable>enable</Nullable>