add :allow_bang :params to @ explanation of VariableRebinding check

[SpaceEEC]

The :allow_bang option wasn't added to :params of the @explanation attribute of Credo.Check.Refactor.VariableRebinding resulting in the option/parameter not being included in the configuration options:

┃    __ CONFIGURATION OPTIONS
┃
┃       You can disable this check by using this tuple
┃
┃         {Credo.Check.Refactor.VariableRebinding, false}
┃
┃       There are no other configuration options.

After adding the option the output is as expected:

┃    __ CONFIGURATION OPTIONS
┃
┃       To configure this check, use this tuple
┃
┃         {Credo.Check.Refactor.VariableRebinding, <params>}
┃
┃       with <params> being false or any combination of these keywords:
┃
┃         allow_bang:            Variables with a bang suffix will be ignored.

[rrrene]

@SpaceEEC Thx! 👍