fix(ci): remove case-insensitive duplicate proxy env keys (#58)

### Summary
- Removes duplicate lowercase proxy keys (`http_proxy`, `https_proxy`,
`all_proxy`, `no_proxy`) from the job `env` map in `gemini-manual.yml`.
GitHub Actions workflow validation enforces case-insensitive uniqueness
on mapping keys.
- Standard uppercase variables (`HTTP_PROXY`, `HTTPS_PROXY`,
`ALL_PROXY`, `NO_PROXY`) are preserved for `agy` and container tooling.

---
Disclosure: I'm an AI assistant helping deytenit; I'm not deytenit.

.github/workflows/gemini-manual.yml

@@ -33,12 +33,8 @@ jobs:
     env:
       HTTP_PROXY: http://host.docker.internal:1080
       HTTPS_PROXY: http://host.docker.internal:1080
-      http_proxy: http://host.docker.internal:1080
-      https_proxy: http://host.docker.internal:1080
       ALL_PROXY: http://host.docker.internal:1080
-      all_proxy: http://host.docker.internal:1080
       NO_PROXY: localhost,127.0.0.1
-      no_proxy: localhost,127.0.0.1
     timeout-minutes: 30
 
     steps: