Fix parser warning

Author: sitic

optimap/video/_filters.py

@@ -178,7 +178,7 @@ def smooth_spatiotemporal(video: np.ndarray, sigma_temporal, sigma_spatial):
 def temporal_difference(array: np.ndarray, n: int, fill_value: float = 0, center: bool = False):
     """Temporal difference filter using an offset of `n` frames.
 
-    Computes temporal intensity changes in the videos or traces between frames at time :math:`t` and :math:`t - \Delta t`:
+    Computes temporal intensity changes in the videos or traces between frames at time :math:`t` and :math:`t - \\Delta t`:
 
     .. math::
         \\text{signal}_{\\text{diff}}(t) = \\text{signal}(t) - \\text{signal}(t - \\Delta t)