chore: remove duplicate plotting code (#639)

## Description
Removing duplicate plotting code, see lines 936-968


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Author: VeraChristina

training/src/anemoi/training/diagnostics/callbacks/plot.py

@@ -1070,41 +1070,6 @@ def _plot(
             )
 
 
-class BasePlotAdditionalMetrics(BasePerBatchPlotCallback):
-    """Base processing class for additional metrics."""
-
-    def process(
-        self,
-        pl_module: pl.LightningModule,
-        outputs: list,
-        batch: torch.Tensor,
-    ) -> tuple[np.ndarray, np.ndarray]:
-        if self.latlons is None:
-            self.latlons = np.rad2deg(pl_module.latlons_data.clone().detach().cpu().numpy())
-
-        input_tensor = (
-            batch[
-                :,
-                pl_module.multi_step - 1 : pl_module.multi_step + pl_module.rollout + 1,
-                ...,
-                pl_module.data_indices.data.output.full,
-            ]
-            .detach()
-            .cpu()
-        )
-        data = self.post_processors(input_tensor)[self.sample_idx]
-        output_tensor = torch.cat(
-            tuple(
-                self.post_processors(x[:, ...].detach().cpu(), in_place=False)[self.sample_idx : self.sample_idx + 1]
-                for x in outputs[1]
-            ),
-        )
-        output_tensor = pl_module.output_mask.apply(output_tensor, dim=2, fill_value=np.nan).numpy()
-        data[1:, ...] = pl_module.output_mask.apply(data[1:, ...], dim=2, fill_value=np.nan)
-        data = data.numpy()
-        return data, output_tensor
-
-
 class PlotSpectrum(BasePlotAdditionalMetrics):
     """Plots TP related metric comparing target and prediction.