Fixes duplicated text in pip installation docs (#3969)

In the [Local Installation / Installation using Isaac Lab Pip Packages
page](https://isaac-sim.github.io/IsaacLab/main/source/setup/installation/isaaclab_pip_installation.html#installing-dependencies)
of the documentation, the “Installing dependencies” section is broken. I
removed duplicate content and corrected the ordering.

Fixes #3967

- Documentation update

| Before | After |
| ------ | ----- |
| <img width="823" height="999" alt="スクリーンショット 2025-11-08 012827"
src="https://github.com/user-attachments/assets/6f022810-cff5-44c6-a835-75bc780433ce"
/> | <img width="822" height="651" alt="スクリーンショット 2025-11-08 014930"
src="https://github.com/user-attachments/assets/c06eacf1-bd4a-4210-8a79-c64fc923c622"
/> |

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

Author: shryt

CONTRIBUTORS.md

@@ -123,6 +123,7 @@ Guidelines for modifications:
 * Ritvik Singh
 * Rosario Scalise
 * Ryley McCarroll
+* Sahara Yuta
 * Sergey Grizan
 * Shafeef Omar
 * Shaoshu Su