Adds matplotlib-inline to license exceptions (#3853)

matplotlib-inline has BSD-3 license, so it's ok for us to include it. We
already have the license file specified for it.

- Documentation update

- [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`
- [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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Author: kellyguo11

.github/workflows/license-exceptions.json

@@ -435,5 +435,10 @@
     "package": "onnx-ir",
     "license": "UNKNOWN",
     "comment": "Apache 2.0"
+  },
+  {
+    "package": "matplotlib-inline",
+    "license": "UNKNOWN",
+    "comment": "BSD-3"
   }
 ]