Cleanup dependencies #1107

[thompson-tomo]

Closes #1107

[Copilot]

Pull Request Overview

This PR cleans up project dependencies by organizing package references and consolidating their format. The changes improve the consistency of dependency declarations across multiple EventFlow projects.

• Moved Microsoft.CSharp to a conditional target framework group for better organization
• Simplified package reference formatting by using inline Version attributes
• Reorganized conditional dependency groups for clarity

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Source/EventFlow/EventFlow.csproj	Moved Microsoft.CSharp to netstandard2.1 conditional group and simplified JetBrains.Annotations format
Source/EventFlow.Sql/EventFlow.Sql.csproj	Added conditional group for netstandard2.0 dependencies
Source/EventFlow.EntityFramework/EventFlow.EntityFramework.csproj	Simplified Microsoft.EntityFrameworkCore package reference format

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}