Do not delete empty storage

This MR aims to remove the deletion of the code and storage associated to an implicit account, while emptying it's balance. As implicit accounts do not have such code or storage, the calls to remove were useless (nothing removed), but were generating some gas consumption as the access to the storage was carbonated. Emptying an implicit account is not accounting extra gas cost any more.

Additionally, it updates a test to conform to the new behaviour.

Manually testing the MR

Run the tests

Fixes: #3188 (closed)

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR