Do not force "operator-assignment" syntax

[okovpashko]

I'd suggest updating the "operator-assignment" rule not to force using of the += operator. It is no more than a personal preference and we should not force using a particular syntax.

Example

let accumulator = '';

accumulator = accumulator + 'some value'; // error: Assignment (=) can be replaced with operator assignment (+=)

Actual result: linting error
Expected result: no lining errors

[hraboviyvadim]

Agree, it might be a good idea to add rules like this locally to your project if you want.