[HOTFIX] Only check headers of NIfTI files
[HOTFIX] Only check headers of NIfTI files

We are writing CIfTI2 timeseries with extension .dtseries.nii. They break the DerivativesDataSink.
poldracklab/niworkflows,poldracklab/niworkflows,oesteban/niworkflows,oesteban/niworkflows,oesteban/niworkflows