Generating dashboard page takes too long when table `action` contains
many records and error log contains message like
```
2025/04/21 21:21:07 ...activities/action.go:470:GetFeeds() [W] [Slow SQL Query] SELECT `action`.* FROM `action` INNER JOIN `repository` ON `repository`.id = `action`.repo_id WHERE user_id=? AND is_deleted=? ORDER BY `action`.`created_unix` DESC LIMIT 20 [12 false] - 2m8.393454675s
```
This mod removes unnecessary inner join like proposed
in https://github.com/go-gitea/gitea/pull/32127
For complete solution index(user_id, is_deleted) for action table
should be created also like in https://github.com/go-gitea/gitea/pull/32333
(not included in this mod).
Related: https://github.com/go-gitea/gitea/pull/32127
Related: https://github.com/go-gitea/gitea/pull/32333
Author-Change-Id: IB#1160173
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### Tests
- I added test coverage for Go changes...
- [x] in their respective `*_test.go` for unit tests.
- [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
- [ ] in `web_src/js/*.test.js` if it can be unit tested.
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- [x] I did not document these changes and I do not expect someone else to do it.
### Release notes
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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7604
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Paweł Bogusławski <pboguslawski@noreply.codeberg.org>
Co-committed-by: Paweł Bogusławski <pboguslawski@noreply.codeberg.org>
7380eac5a2