[sonic-platform-daemons] Update submodule (#8165)

To include:
> 66e7817 2021-07-13 [pcied] Fix pcied failure to load due to 'pcied NameError: name 'self' is not defined' (sonic-net/sonic-platform-daemons#198) 
> 3df6757 2021-07-08 [ci] fix result color bar in the code coverage report (sonic-net/sonic-platform-daemons#196)