Fix vectorization issue in rbend

[cr-xu]

• Fix Vectorization error in RBend #171 . The RBend construction method was not properly updated with the vectorization feature Vectorised simulations #116
• Fix a comment in Dipole to clearly mention that by default a sector bend is generated.

Description

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist

• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have reformatted the code and checked that formatting passes (required).
• I have have fixed all issues found by flake8 (required).
• I have ensured that all pytest tests pass (required).
• I have run pytest on a machine with a CUDA GPU and made sure all tests pass (required).
• I have checked that the documentation builds (required).

Note: We are using a maximum length of 88 characters per line

[jank324]

Suggested change

	# non_zero_mask = self.length != 0
	# value[non_zero_mask] = self.angle[non_zero_mask] / self.length[non_zero_mask]

[jank324]

Or is there a reason those comments should be there?

[jank324]

Also, the PR number should be added to the changelog entry.

[jank324]

@cr-xu if you didn't have an important reason to keep the comment, I think this PR can now just be merged as is.

[cr-xu]

Thanks for the changes! I forgot to remove the comments.