Use 9.0 LangVersion as 10.0 causes some compile issues

Author: bahusoid

build-common/NHibernate.props

@@ -6,6 +6,7 @@
     <VersionPatch  Condition="'$(VersionPatch)'  == ''">0</VersionPatch>
     <!-- Clear VersionSuffix for making release and set it to dev for making development builds -->
     <VersionSuffix Condition="'$(VersionSuffix)' == ''">dev</VersionSuffix>
+    <LangVersion Condition="'$(MSBuildProjectExtension)' != '.vbproj'">9.0</LangVersion>
 
     <VersionPrefix Condition="'$(VersionPrefix)' == ''">$(NhVersion).$(VersionPatch)</VersionPrefix>
     <VersionSuffix Condition="'$(VersionSuffix)' != '' AND '$(BuildNumber)' != ''">$(VersionSuffix).$(BuildNumber)</VersionSuffix>

src/NHibernate/NHibernate.csproj

@@ -12,7 +12,6 @@
 
     <PackageDescription>NHibernate is a mature, open source object-relational mapper for the .NET framework. It is actively developed, fully featured and used in thousands of successful projects.</PackageDescription>
     <PackageTags>ORM; O/RM; DataBase; DAL; ObjectRelationalMapping; NHibernate; ADO.Net; Core</PackageTags>
-    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>