Show the ScalarData match in the related types example

The surrounding text says Error is not Data, Scalar, or ScalarData, but
the example only demonstrated the first two. Add the ScalarData check so
the example covers every type the sentence claims, matching the
equivalent section on the Binary page.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Michael Harp <mike@mikeharp.com>

Author: miharp

docs/_openvox_8x/lang_data_error.md

@@ -118,6 +118,7 @@ $e = Error('boom')
 notice($e =~ RichData)   # true
 notice($e =~ Data)       # false
 notice($e =~ Scalar)     # false
+notice($e =~ ScalarData) # false
 ```
 
 That matters when a parameter or function expects `Data`, which covers only the JSON-compatible types. Use