fix: typo

Author: lymichelle21

examples/06_Combining Models.ipynb

@@ -13,7 +13,7 @@
    "source": [
     "This section demonstrates how prognostic models can be combined. There are two instances in which this is useful: \n",
     "\n",
-    "1. Combining multiple models of different inter-related systems into one system-of-system model** (i.e., [Composite Models](https://nasa.github.io/progpy/api_ref/prog_models/CompositeModel.html)), or\n",
+    "1. Combining multiple models of different inter-related systems into one system-of-system model (i.e., [Composite Models](https://nasa.github.io/progpy/api_ref/prog_models/CompositeModel.html)), or\n",
     "2. Combining multiple models of the same system to be simulated together and aggregated (i.e., [Ensemble Models](https://nasa.github.io/progpy/api_ref/prog_models/EnsembleModel.html) or [Mixture of Expert Models](https://nasa.github.io/progpy/api_ref/progpy/MixtureOfExperts.html)). This is generally done to improve the accuracy of prediction when you have multiple models that each represent part of the behavior or represent a distribution of different behaviors. \n",
     "\n",
     "These two methods for combining models are described in the following sections."