Revert "Build(deps): Bump Microsoft.CodeAnalysis.CSharp from 4.5.0 to 4.8.0 (#14017)"

This reverts commit 1e1bbe7.

Author: yaira2

src/Files.Core.SourceGenerator/Files.Core.SourceGenerator.csproj

@@ -11,7 +11,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.8.0" PrivateAssets="all" />
+        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.5.0" PrivateAssets="all" />
         <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
         <PackageReference Include="PolySharp" Version="1.13.2"  PrivateAssets="all" IncludeAssets="runtime; build; native; contentfiles; analyzers; buildtransitive" />
     </ItemGroup>