MNT: Set explicit niworkflows requirement

Author: effigies

setup.cfg

@@ -32,7 +32,7 @@ install_requires =
     nibabel >=3.1.0
     nipype >=1.5.1,<2.0
     traits <6.4
-    niworkflows @ git+https://github.com/nipreps/niworkflows.git@master
+    niworkflows >= 1.7.0
     nitransforms >= 21.0.0
     numpy >= 1.21.0
     pybids >= 0.15.1