[submodule] Update submodule sonic-dash-api to the latest HEAD automa…

…tically (sonic-net#18017)

#### Why I did it
src/sonic-dash-api
```
* ec15bc7 - (HEAD -> master, origin/master, origin/HEAD) Revert "rename VnetMapping.action_type" (#17) (2 hours ago) [Ze Gan]
* ad0f59e - Add unspecified default value to all enums (2 days ago) [Lawrence Lee]
*   dd844b1 - Merge branch 'add-enum-default' of github.com:theasianpianist/sonic-dash-api into add-enum-default (4 days ago) [Lawrence Lee]
|\  
| * 4b31135 - Merge branch 'master' into add-enum-default (4 days ago) [Lawrence Lee]
* | 4b41ea7 - rename VnetMapping.action_type (4 days ago) [Lawrence Lee]
|/  
* b1ab99f - Add unspecified default value to all enums (4 days ago) [Lawrence Lee]
```
#### How I did it
#### How to verify it
#### Description for the changelog