[submodule] Update submodule sonic-stp to the latest HEAD automatically (sonic-net#21743)

#### Why I did it
src/sonic-stp
```
* 29eb387 - (HEAD -> master, origin/master, origin/HEAD) Fixing compilaion error for marvell_armhf (sonic-net#47) (9 hours ago) [Divya Kumaran Chandralekha]
* b7da558 - Merge pull request sonic-net#44 from wajahatrazi/stp_co_pr (3 days ago) [Divya Kumaran Chandralekha]
|\ 
| failure_prs.log skip_prs.log 47e1e77 - Merge branch 'master' into stp_co_pr (3 days ago) [Divya Kumaran Chandralekha]
| |\ 
| |/ 
|/| 
* | 6e4a94f - Merge pull request sonic-net#46 from divyachandralekha/pvst_pr_1 (4 days ago) [Divya Kumaran Chandralekha]
|\ \ 
| failure_prs.log skip_prs.log | aa5e824 - libevent explicit building dependency removed (4 days ago) [Divya Chandralekha]
|/ / 
* | 9345e5a - Merge pull request sonic-net#43 from omaaartamer/fix/alignment-warnings (5 days ago) [Divya Kumaran Chandralekha]
* | eedb772 - [stp] Add memory alignment padding to structures (9 weeks ago) [omaaartamer]
* | 128e53d - fix: resolve STP alignment warnings (9 weeks ago) [omaaartamer]
 / 
* 30febfa - Fixing changes in the code (9 weeks ago) [Wajahat Razi]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld