Fix docstring indentation in newly added trajectory Python bindings

[sea-bass]

This is weird, but the changes in #2411 that merged without issue ended up breaking the moveit2_tutorials repo with this htmlproofer error:

Warning, treated as error:
docstring of moveit.core.robot_trajectory.PyCapsule.apply_ruckig_smoothing:2:Block quote ends without a blank line; unexpected unindent.
Error: Process completed with exit code 2.

See https://github.com/ros-planning/moveit2_tutorials/actions/runs/6617124169/job/17972803048?pr=796#step:7:20084

I think it has to do with the indents added to the block quotes in some of the new functionality added in this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (faa4795) 50.35% compared to head (c5a9474) 50.43%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2471      +/-   ##
==========================================
+ Coverage   50.35%   50.43%   +0.08%     
==========================================
  Files         390      390              
  Lines       31954    31954              
==========================================
+ Hits        16087    16112      +25     
+ Misses      15867    15842      -25     

Files	Coverage Δ
.../moveit_core/robot_trajectory/robot_trajectory.cpp	77.15% <ø> (ø)

... and 5 files with indirect coverage changes

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