Bump version to 5.2.1 in Edi.Captcha.csproj

Updated the project version from 5.2.0 to 5.2.1 to prepare for a new release.

Author: EdiWang

src/Edi.Captcha/Edi.Captcha.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <TargetFrameworks>net8.0;net9.0</TargetFrameworks>
-        <Version>5.2.0</Version>
+        <Version>5.2.1</Version>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <Company>edi.wang</Company>
         <Authors>Edi Wang</Authors>