ARROW-13458 [C++][Docs] Typo in RecordBatch::schema

Fix typo in docs for RecordBatch::schema

Closes #10811 from rvernica/patch-4

Authored-by: rvernica <rvernica@gmail.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>

cpp/src/arrow/record_batch.h

@@ -85,8 +85,7 @@ class ARROW_EXPORT RecordBatch {
   /// \brief Determine if two record batches are approximately equal
   bool ApproxEquals(const RecordBatch& other) const;
 
-  // \return the table's schema
-  /// \return true if batches are equal
+  /// \return the record batch's schema
   const std::shared_ptr<Schema>& schema() const { return schema_; }
 
   /// \brief Retrieve all columns at once