docs: add tensorrt description in docstring.

Author: GdoongMathew

src/lightning/pytorch/utilities/testing/_runif.py

@@ -65,6 +65,7 @@ def _runif_reasons(
         psutil: Require that psutil is installed.
         sklearn: Require that scikit-learn is installed.
         onnx: Require that onnx is installed.
+        tensorrt: Require that torch-tensorrt is installed.
 
     """