fix(system_error_monitor): fix dying node

[takayuki5168]

Description

Currently, system_error_monitor died with the following error due to the time resource is different.
what(): can't subtract times with different time sources [1 != 2]

related discussion: https://answers.ros.org/question/380328/robot_localization-cant-subtract-times-with-different-time-sources/

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[takayuki5168]

I confirmed that system_error_monitor does not die with this PR on the planning simulator.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01 ⚠️

Comparison is base (f210e40) 11.92% compared to head (89504cf) 11.92%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3103      +/-   ##
==========================================
- Coverage   11.92%   11.92%   -0.01%     
==========================================
  Files        1332     1332              
  Lines       92934    92937       +3     
  Branches    24735    24735              
==========================================
  Hits        11079    11079              
- Misses      70376    70379       +3     
  Partials    11479    11479              

Flag	Coverage Δ		*Carryforward flag
differential	0.00% <0.00%> (?)
total	11.92% <ø> (ø)		Carriedforward from f210e40

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
...em_error_monitor/src/system_error_monitor_core.cpp	0.00% <0.00%> (ø)

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[ito-san]

Verified this issue was gone by this fix.