Fix regression from commit cfcc08b

Motivation:

Commit cfcc08b introduced a problem because the term `x-ray probe`
was mistakenly added as `X-ray probe`

Modification:

Update term to use the correct lower-case `x`, to be consistent with
existing use.

Result:

We can now build PaNET again.

Author: paulmillar

source/PaNET.csv

@@ -386,6 +386,6 @@ ID number,,,,,,,,,,,,,,,,,,
 1329,http://purl.org/pan-science/PaNET/PaNET01329,kossel lines,,,,,owl:Class,subclass,divergent beam diffraction,x-ray fluorescence,,,,,,,,
 1330,http://purl.org/pan-science/PaNET/PaNET01330,diffuse multiple scattering,,,,,owl:Class,subclass,divergent beam diffraction,diffuse scattering,,,,,,,,
 1331,http://purl.org/pan-science/PaNET/PaNET01331,MHz x-ray microscopy,,,X-ray microscopy that operates on time scales less than one microsecond with femtosecond illumination,https://doi.org/10.1364/OPTICA.6.001106,owl:Class,subclass,x-ray microscopy,hard x-ray probe,versus time ultrafast,pulsed probe,single shot technique,,,,,
-1332,http://purl.org/pan-science/PaNET/PaNET01332,x-ray propagation phase contrast tomography,,,,,owl:Class,subclass,propagation phase contrast tomography,X-ray probe,,,,,,,,
+1332,http://purl.org/pan-science/PaNET/PaNET01332,x-ray propagation phase contrast tomography,,,,,owl:Class,subclass,propagation phase contrast tomography,x-ray probe,,,,,,,,
 1333,http://purl.org/pan-science/PaNET/PaNET01333,x-ray propagation phase contrast microtomography,PPC-SrμCT,,,,owl:Class,subclass,x-ray propagation phase contrast tomography,,,,,,,,,
 ,,Create dataset instances and give them hasTechnique relationship to instances of techniques. Can then use reasoner to search for individuals based on 'hasTechnique some technique' where technique is any of the technique classes above.,,,,,,,,,,,,,,,,