chore: pin latest commit on tsalo/niworkflows/sbref branch

Confirms that the

```
fMRIPrep failed: name 'is_container' is not defined
```
is gone.

Author: oesteban

fmriprep/workflows/bold/base.py

@@ -17,7 +17,7 @@
 from nipype.pipeline import engine as pe
 from nipype.interfaces import utility as niu
 
-from niworkflows.utils.misc import select_first
+from niworkflows.utils.connections import pop_file
 
 from ...utils.meepi import combine_meepi_source
 
@@ -153,7 +153,7 @@ def init_func_preproc_wf(bold_file):
     output_dir = str(config.execution.output_dir)
 
     # Extract BIDS entities and metadata from bold reference file
-    ref_file = select_first(bold_file)
+    ref_file = pop_file(bold_file)
     layout = config.execution.layout
     entities = layout.parse_file_entities(ref_file)
     metadata = layout.get_metadata(ref_file)

setup.cfg

@@ -27,7 +27,7 @@ install_requires =
     nipype >= 1.5
     nitime
     nitransforms >= 20.0.0rc3,<20.2
-    niworkflows @ git+https://github.com/tsalo/niworkflows.git@9d78796373163d2881f80407ff9d5aee9c65f77e
+    niworkflows @ git+https://github.com/tsalo/niworkflows.git@6fe250cb8db9b79672ba9d28a4adb15fc83e2f0f
     numpy
     pandas
     psutil >= 5.4