Change linc mode default file format to CIFTI

[tsalo]

Closes none, but addresses a request by @sattertt.

Changes proposed in this pull request

• Change the default file format for "linc" mode from NIfTI to CIFTI.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.10%. Comparing base (de25e03) to head (cfc2707).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1248   +/-   ##
=======================================
  Coverage   84.10%   84.10%           
=======================================
  Files          59       59           
  Lines        7210     7210           
  Branches     1064     1064           
=======================================
  Hits         6064     6064           
  Misses        882      882           
  Partials      264      264           

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