JP-3800 update dark current documentation to remove confusing stateme…

…nt about bias subtraction (#8955)

docs/jwst/dark_current/description.rst

@@ -6,8 +6,7 @@ Description
 
 Assumptions
 -----------
-It is assumed that the input science data have *NOT* had the zero group (or
-bias) subtracted. We also do not want the dark subtraction process to remove
+We do not want the dark subtraction process to remove
 the bias signal from the science exposure, therefore the dark reference data
 should have their own group zero subtracted from all groups. This means that
 group zero of the dark reference data will effectively be zero-valued.