fix(backend): Remove croniter (#9130)

Croniter is unused, and it will be deprecated soon.

### Changes 🏗️

Remove croniter.

### Checklist 📋

#### For code changes:
- [ ] I have clearly listed my changes in the PR description
- [ ] I have made a test plan
- [ ] I have tested my changes according to the test plan:
  <!-- Put your test plan here: -->
  - [ ] ...

<details>
  <summary>Example test plan</summary>
  
  - [ ] Create from scratch and execute an agent with at least 3 blocks
- [ ] Import an agent from file upload, and confirm it executes
correctly
  - [ ] Upload agent to marketplace
- [ ] Import an agent from marketplace and confirm it executes correctly
  - [ ] Edit an agent from monitor, and confirm it executes correctly
</details>

#### For configuration changes:
- [ ] `.env.example` is updated or already compatible with my changes
- [ ] `docker-compose.yml` is updated or already compatible with my
changes
- [ ] I have included a list of my configuration changes in the PR
description (under **Changes**)

<details>
  <summary>Examples of configuration changes</summary>

  - Changing ports
  - Adding new services that need to communicate with each other
  - Secrets or environment variable changes
  - New or infrastructure changes such as databases
</details>

Co-authored-by: Swifty <[email protected]>

autogpt_platform/backend/pyproject.toml

@@ -14,7 +14,6 @@ anthropic = "^0.40.0"
 apscheduler = "^3.11.0"
 autogpt-libs = { path = "../autogpt_libs", develop = true }
 click = "^8.1.7"
-croniter = "^5.0.1"
 discord-py = "^2.4.0"
 e2b-code-interpreter = "^1.0.1"
 fastapi = "^0.115.5"