refactor: remove duplicate Commit() declaration from PendingUpdate template

Remove Commit() from PendingUpdate<T> since it's already declared in
PendingUpdateBase with full documentation. The template class inherits
it automatically.

This follows DRY principle and avoids maintaining duplicate documentation.

Author: shangxinli

src/iceberg/pending_update.h

@@ -87,14 +87,6 @@ class ICEBERG_EXPORT PendingUpdate : public PendingUpdateBase {
   ///         - InvalidArgument: if pending changes are conflicting
   virtual Result<T> Apply() = 0;
 
-  /// \brief Apply and commit the pending changes to the table
-  ///
-  /// \return Status::OK if the commit was successful, or an error:
-  ///         - ValidationFailed: if update cannot be applied to current metadata
-  ///         - CommitFailed: if update cannot be committed due to conflicts
-  ///         - CommitStateUnknown: if commit success state is unknown
-  Status Commit() override = 0;
-
  protected:
   PendingUpdate() = default;
 };