[submodule] Update submodule sonic-platform-common to the latest HEAD…

… automatically (#14740)

#### Why I did it
src/sonic-platform-common
```
* 6e44c97 - (HEAD -> 202012, origin/202012) Change Y cable simulator log level from error to warning due to false alarm (3 months ago) [ShiyanWangMS]
* df020b8 - Add missing sys imports (#343) (6 months ago) [spilkey-cisco]
* cb00d2e - Use github code scanning instead of LGTM (#328) (7 months ago) [Liu Shilong]
* dd74113 - [ssd_generic] Fix innodisk health regex (#287) (9 months ago) [Alexander Allen]
```