Fixed memory leak in spectroscopy code

[sofiemartins]

For each configuration that is analyzed, there are temporary fields allocated in init_propagator_eo(), but not all of them are freed, so after analyzing a certain amount of configuration, the system runs out of memory.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 49.64%. Comparing base (8bf5685) to head (9e4bf49).
Report is 7 commits behind head on HiRep-CUDA.

Files with missing lines	Patch %	Lines
LibHR/Observables/calc_prop.c	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           HiRep-CUDA     #120   +/-   ##
===========================================
  Coverage       49.64%   49.64%           
===========================================
  Files             383      383           
  Lines           58981    58987    +6     
  Branches        11390    11392    +2     
===========================================
+ Hits            29283    29287    +4     
+ Misses          26846    26845    -1     
- Partials         2852     2855    +3     

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