Adds instruction to update pip (#102)

# Description

Due to large Isaac Sim pip packages, pip installation is only possible
with the latest pip version 24. This MR adds a note in the pip
installation documentation to update pip to the latest version.

## Type of change

<!-- As you go through the list, delete the ones that are not
applicable. -->

- Bug fix (non-breaking change which fixes an issue)


## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] 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
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

<!--
As you go through the checklist above, you can mark something as done by
putting an x character in it

For example,
- [x] I have done this task
- [ ] I have not done this task
-->

docs/source/setup/installation/pip_installation.rst

@@ -74,6 +74,12 @@ compatibility issues with some Linux distributions. If you encounter any issues,
 
             pip install torch==2.4.0 --index-url https://download.pytorch.org/whl/cu121
 
+-  Before installing Isaac Sim, ensure the latest pip version is installed. To update pip, run
+
+   .. code-block:: bash
+
+      pip install --upgrade pip
+
 
 -  Then, install the Isaac Sim packages necessary for running Isaac Lab: