Correct documentation regarding Freesurfer

[tsalo]

Closes none, but makes it clear that Freesurfer derivatives are no longer used.

Also addresses issues stemming from PennLINC/xcpd_build#28, PennLINC/xcpd_build#29, PennLINC/xcpd_build#30, PennLINC/xcpd_build#31, PennLINC/xcpd_build#33, PennLINC/xcpd_build#35, PennLINC/xcpd_build#36, PennLINC/xcpd_build#37, PennLINC/xcpd_build#38, and PennLINC/xcpd_build#39.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 78.63%. Comparing base (b766391) to head (b6c0a70).
Report is 41 commits behind head on main.

Files with missing lines	Patch %	Lines
xcp_d/interfaces/ants.py	66.66%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1277      +/-   ##
==========================================
+ Coverage   78.55%   78.63%   +0.08%     
==========================================
  Files          59       59              
  Lines        7312     7308       -4     
  Branches     1105     1106       +1     
==========================================
+ Hits         5744     5747       +3     
+ Misses       1279     1273       -6     
+ Partials      289      288       -1     

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[tsalo]

The last round of changes to the build image (PennLINC/xcpd_build#38) didn't fix the problem:

3dReHo: error while loading shared libraries: libgsl.so.0: cannot open shared object file: No such file or directory

[tsalo]

Finally!!! Also, ANTS changed the filename template for CompositeTransformUtil, so I had to make a modified version of the interface instead of importing it from nipype.