Update sonic-swss-common submodule (#12578)

#### Why I did it
Submodule update for sonic-swss-common with following change:
```
276f47c [sonic-db-cli] Fix sonic-db-cli crash when database config file not ready issue. (#639)
```

#### How I did it

#### How to verify it

#### Which release branch to backport (provide reason below if selected)

<!--
- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
- e.g.
- [x] 202006
-->

- [ ] 201811
- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106

#### Description for the changelog
Submodule update for sonic-swss-common with following change:
276f47c [sonic-db-cli] Fix sonic-db-cli crash when database config file not ready issue. (#639)


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