Fix typo in SAGPool (#5244)

* Fix typo in SAGPool

Removed a piece of text belonging to the top-k operator.

* Update torch_geometric/nn/pool/sag_pool.py

Co-authored-by: Padarn Wilson <padarn.wilson@grabtaxi.com>

Co-authored-by: Matthias Fey <matthias.fey@tu-dortmund.de>
Co-authored-by: Padarn Wilson <padarn.wilson@grabtaxi.com>

torch_geometric/nn/pool/sag_pool.py

@@ -34,10 +34,8 @@ class SAGPooling(torch.nn.Module):
 
             \mathbf{X}^{\prime} &= (\mathbf{X} \odot \mathbf{y})_{\mathbf{i}}
 
-            \mathbf{A}^{\prime} &= \mathbf{A}_{\mathbf{i},\mathbf{i}},
+            \mathbf{A}^{\prime} &= \mathbf{A}_{\mathbf{i},\mathbf{i}}.
 
-    where nodes are dropped based on a learnable projection score
-    :math:`\mathbf{p}`.
     Projections scores are learned based on a graph neural network layer.
 
     Args: