fix: display actual tolerance in CofR error message (#2296)

Improves error message by showing the tolerance value that was used,
making it easier for users to understand what needs adjustment.

Fixes #2295

Co-authored-by: Chu Julung <chujulung@ChudeMacBook-Air.local>

Author: Simon99

Wrappers/Python/cil/processors/CofR_image_sharpness.py

@@ -194,7 +194,7 @@ def gss(self, data, ig, search_range, tolerance, binning):
                 new_point = sample_points[-1]- step_c
 
             else:
-                raise ValueError("The centre of rotation could not be located to the requested tolerance. Try increasing the search tolerance.")
+                raise ValueError(f"The centre of rotation could not be located to the requested tolerance ({tolerance:.6f} pixels). Try increasing the search tolerance.")
 
             if interval < tolerance:
                 break