Updated typo in pointcloud.cpp for tensor (#6228)

The documentation through sphinx had incorrect format for example code of `extrude_linear` function.

cpp/pybind/t/geometry/pointcloud.cpp

@@ -655,6 +655,7 @@ The implementation is inspired by the PCL implementation. Reference:
 Example:
 
     This code generates a set of straight lines from a point cloud::
+        
         import open3d as o3d
         import numpy as np
         pcd = o3d.t.geometry.PointCloud(np.random.rand(10,3))