Merged PR 50991: [release/8.0] Use live version of S.T.J in analyzers

#### AI description  (iteration 1)
#### PR Classification
Configuration update that ensures analyzers use the live version of System.Text.Json.

#### PR Summary
This PR modifies the `/eng/Versions.props` file to dynamically reference the live System.Text.Json version instead of a fixed version.
- `/eng/Versions.props`: Replaced the hard-coded `<AnalyzersSystemTextJsonVersion>8.0.5</AnalyzersSystemTextJsonVersion>` with `$(SystemTextJsonVersion)`.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

Author: wtgodbe

eng/Versions.props

@@ -200,7 +200,7 @@
     <MicrosoftVSSDKBuildToolsVersion>15.9.3032</MicrosoftVSSDKBuildToolsVersion>
     <!-- Manually updated version from 6.0.0 to address CVE-2021-43877 -->
     <RepoTasksSystemSecurityCryptographyXmlVersion>6.0.1</RepoTasksSystemSecurityCryptographyXmlVersion>
-    <AnalyzersSystemTextJsonVersion>8.0.5</AnalyzersSystemTextJsonVersion>
+    <AnalyzersSystemTextJsonVersion>$(SystemTextJsonVersion)</AnalyzersSystemTextJsonVersion>
     <!-- Stable dotnet/corefx packages no longer updated for .NET Core 3 -->
     <MicrosoftCSharpVersion>4.7.0</MicrosoftCSharpVersion>
     <MicrosoftWin32RegistryVersion>5.0.0</MicrosoftWin32RegistryVersion>