docs(reference): regenerate env-vars page for shifted source line

The doc-comments commit on MTConnect-Compliance-Tests shifted the line
of the FixtureDirEnv read in CppAgentParityWorkflowTests.cs from 488 to
499. The generated page embeds source line numbers, so the change
desynced docs/reference/environment-variables.md and the in-sync test
in MTConnect.NET-Docs-Tests failed on every integration branch layered
on top of this PR (#185, #186).

Author: ottobolyos

docs/reference/environment-variables.md

@@ -84,7 +84,7 @@ Every environment-variable reference discovered in the source tree. Both the C#
 
 | Kind | Source | Default / value | Context |
 | --- | --- | --- | --- |
-| `csharp-read` | [`tests/Compliance/MTConnect-Compliance-Tests/L2_CrossImpl/CppAgentParityWorkflowTests.cs:488`](https://github.com/TrakHound/MTConnect.NET/blob/master/tests/Compliance/MTConnect-Compliance-Tests/L2_CrossImpl/CppAgentParityWorkflowTests.cs#L488) |  | = Environment.GetEnvironmentVariable(FixtureDirEnv) |
+| `csharp-read` | [`tests/Compliance/MTConnect-Compliance-Tests/L2_CrossImpl/CppAgentParityWorkflowTests.cs:499`](https://github.com/TrakHound/MTConnect.NET/blob/master/tests/Compliance/MTConnect-Compliance-Tests/L2_CrossImpl/CppAgentParityWorkflowTests.cs#L499) |  | = Environment.GetEnvironmentVariable(FixtureDirEnv) |
 
 Adding a new `Environment.GetEnvironmentVariable("…")` call, a new `${MTCONNECT_…}` read in a contributor script, or a new `$env:MTCONNECT_…` reference in a PowerShell script without regenerating this page fails the validation test in CI.