[Test] Move extra.yaml to the correct directory

[speth]

The interfaces/cython/cantera/test/data directory is just a copy of the test/data directory, created as part of the build process.

Checklist

• There is a clear use-case for this code change
• The commit message has a short title & references relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• The pull request is ready for review

Changes proposed in this pull request

• Move extra.yaml to test/data

[codecov]

Codecov Report

Merging #813 into master will decrease coverage by 0.17%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #813      +/-   ##
==========================================
- Coverage   71.57%   71.39%   -0.18%     
==========================================
  Files         372      372              
  Lines       44376    43482     -894     
==========================================
- Hits        31760    31045     -715     
+ Misses      12616    12437     -179     

Impacted Files	Coverage Δ
include/cantera/thermo/PDSS.h	0.00% <0.00%> (-100.00%)	⬇️
include/cantera/equil/vcs_MultiPhaseEquil.h	0.00% <0.00%> (-100.00%)	⬇️
include/cantera/equil/MultiPhaseEquil.h	0.00% <0.00%> (-95.00%)	⬇️
include/cantera/thermo/MolalityVPSSTP.h	20.00% <0.00%> (-80.00%)	⬇️
include/cantera/transport/GasTransport.h	20.00% <0.00%> (-80.00%)	⬇️
include/cantera/thermo/SpeciesThermoInterpType.h	20.00% <0.00%> (-70.00%)	⬇️
include/cantera/base/global.h	38.46% <0.00%> (-54.88%)	⬇️
include/cantera/thermo/VPStandardStateTP.h	20.00% <0.00%> (-51.43%)	⬇️
include/cantera/thermo/Phase.h	50.00% <0.00%> (-36.05%)	⬇️
src/clib/Cabinet.h	0.00% <0.00%> (-26.42%)	⬇️
... and 55 more

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