docs(api): drop retired validateOnly from hand-written batch examples (#4052)

The docs-drift-check flagged four hand-written references that still presented
`validateOnly` as a working dry-run option — a `data-api` / `wire-format` batch
example, a `client-sdk` example, and the client-sdk Batch Options table row
("Dry-run mode — validate without persisting"). The key is retired and now 400s,
so these advertised a feature that no longer exists. Removed the key from the
three examples (fixing JSON trailing commas) and deleted the table row. The
generated references already carry the [REMOVED] prescription.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TzLE9cw4gZKNyPN2ZP4iTt

Author: claude

content/docs/api/client-sdk.mdx

@@ -225,7 +225,6 @@ const batchResult = await client.data.batch('account', {
     atomic: true,
     returnRecords: true,
     continueOnError: false,
-    validateOnly: false,
   },
 });
 
@@ -499,7 +498,6 @@ The `find` method accepts an options object with **canonical** (recommended) fie
 | `atomic` | `boolean` | `true` | Rollback entire batch on any failure |
 | `returnRecords` | `boolean` | `false` | Include full records in response |
 | `continueOnError` | `boolean` | `false` | Continue after errors (when atomic=false) |
-| `validateOnly` | `boolean` | `false` | Dry-run mode — validate without persisting |
 
 ---
 

content/docs/api/data-api.mdx

@@ -92,8 +92,7 @@ Execute a batch operation (create / update / upsert / delete) on multiple record
   "options": {
     "atomic": true,
     "returnRecords": true,
-    "continueOnError": false,
-    "validateOnly": false
+    "continueOnError": false
   }
 }
 ```

content/docs/api/wire-format.mdx

@@ -484,8 +484,7 @@ Process many records of a **single** operation type in one request. The body car
   ],
   "options": {
     "atomic": true,
-    "continueOnError": false,
-    "validateOnly": false
+    "continueOnError": false
   }
 }
 ```