Fix rst errors

[christophfroehlich]

Catkin scripts complain

<string>:344: (ERROR/3) Unknown target name: "i_min".
<string>:344: (ERROR/3) Unknown target name: "i_max".
<string>:345: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_term".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_term".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:344: (ERROR/3) Unknown target name: "i_min".
<string>:344: (ERROR/3) Unknown target name: "i_max".
<string>:345: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_gain".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_term".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_term".
<string>:363: (ERROR/3) Unknown target name: "i_error".
<string>:363: (ERROR/3) Unknown target name: "i_error".

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.72%. Comparing base (608f56a) to head (4eb8cd6).
⚠️ Report is 1 commits behind head on ros2-master.

Additional details and impacted files

@@             Coverage Diff              @@
##           ros2-master     #447   +/-   ##
============================================
  Coverage        77.72%   77.72%           
============================================
  Files               29       29           
  Lines             2007     2007           
  Branches           128      128           
============================================
  Hits              1560     1560           
  Misses             379      379           
  Partials            68       68           

Flag	Coverage Δ
unittests	77.72% <ø> (ø)

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