[sonic-platform-common] Update submodule (#8240)

To include:
> e168f1d 2021-07-19 pettershao-ragilenetworks: [python coverage] fix result color bar (sonic-net/sonic-platform-common#202)
> 87c81de 2021-07-13 Prince George: Fix Xcvrd crash due to invalid key access in type_of_media_interface, host_electrical_interface, connector_dict (sonic-net/sonic-platform-common#206)
> 4533f82 2021-06-21 ngoc-do: Add a template function that returns list of asics on module (sonic-net/sonic-platform-common#185)
> 1e860c5 2021-06-18 Aravind Mani: Fix decode error when parsing EEPROM fields (sonic-net/sonic-platform-common#199)
> 93641f3 2021-06-17 Sujin Kang: Unifying the platform api for get_pcie_aer_stats with PcieBase (sonic-net/sonic-platform-common#197)