Fixes GLIBC errors with importing torch before AppLauncher (#560)

# Description

In conda environments, import torch before importing AppLauncher
triggers `version `GLIBCXX_3.4.30' not found` error. This change moves
torch import to be after AppLauncher, which resolves the issue.


## Type of change

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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

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scripts/demos/bipeds.py

@@ -16,7 +16,6 @@ This script demonstrates how to simulate bipedal robots.
 """Launch Isaac Sim Simulator first."""
 
 import argparse
-import torch
 
 from isaaclab.app import AppLauncher
 
@@ -33,6 +32,8 @@ simulation_app = app_launcher.app
 
 """Rest everything follows."""
 
+import torch
+
 import isaaclab.sim as sim_utils
 from isaaclab.assets import Articulation
 from isaaclab.sim import SimulationContext

scripts/demos/quadcopter.py

@@ -16,7 +16,6 @@ This script demonstrates how to simulate a quadcopter.
 """Launch Isaac Sim Simulator first."""
 
 import argparse
-import torch
 
 from isaaclab.app import AppLauncher
 
@@ -33,6 +32,8 @@ simulation_app = app_launcher.app
 
 """Rest everything follows."""
 
+import torch
+
 import isaaclab.sim as sim_utils
 from isaaclab.assets import Articulation
 from isaaclab.sim import SimulationContext