Fix RBend radiation configuration issue in Line.configure_radiation method

[gbrogginess]

Description

This pull request fixes an issue in the Line.configure_radiation method where the radiation_flag attribute was being set on thick RBend elements, causing an AttributeError. The solution adds RBend to the list of element types that are skipped during the iteration over the line.element_dict when configuring radiation. This ensures that only thin elements (or allowed thick elements) have their radiation_flag set, preventing errors when using RBend elements with synchrotron radiation enabled.

Checklist

Mandatory:

• [] I have added tests to cover my changes
• All the tests are passing, including my new ones
• I described my changes in this PR description

Optional:

• The code I wrote follows good style practices (see PEP 8 and PEP 20).
• I have updated the docs in relation to my changes, if applicable
• I have tested also GPU contexts