TAX-2677: docs(tax) - Capitalize ID in PUT 422 response description

Capitalize "id" to "ID" in the 422 error description for the batch
update endpoint, consistent with capitalization elsewhere in the spec.

Refs TAX-2677
Co-Authored-By: Claude <[email protected]>

Author: bc-vincent-zhao

reference/tax_classes.v3.yaml

@@ -148,7 +148,7 @@ paths:
               schema:
                 $ref: '#/components/schemas/ProblemResponseEnvelope'
         '422':
-          description: Validation error (format, duplicate `id` in batch, invalid id values, id-only update payload, etc.).
+          description: Validation error (format, duplicate `id` in batch, invalid ID values, ID-only update payload, etc.).
           content:
             application/problem+json:
               schema: