Fix versioning for beta builds (#245)

Author: Shane32

src/GraphQL.Conventions/GraphQL.Conventions.csproj

@@ -2,8 +2,7 @@
 
   <PropertyGroup>
     <Description>GraphQL Conventions for .NET</Description>
-    <VersionPrefix>7.2.0</VersionPrefix>
-    <PackageVersion>7.2.0</PackageVersion>
+    <VersionPrefix>7.2.0-preview</VersionPrefix>
     <Authors>Tommy Lillehagen</Authors>
     <TargetFrameworks>net6.0;netstandard2.0</TargetFrameworks>
     <LangVersion>9.0</LangVersion>