Fixed matplotlib broken link

Lecture 6/README.md

@@ -10,7 +10,7 @@ To learn more about the dataset, checkout its [registry page](http://registry.ml
 * [**radiant-mlhub**](https://rasterio.readthedocs.io/en/latest/) 
 * [**pandas**](https://pandas.pydata.org/docs/) 
 * [**numpy**](https://numpy.org/doc/) 
-* [**matplotlib**](https://matplotlib.org/stable/contents.html) 
+* [**matplotlib**](https://matplotlib.org/stable/index.html) 
 * [**sklearn**](https://scikit-learn.org/stable/) 
 * [**tensorflow**](https://www.tensorflow.org/api_docs/python/tf/all_symbols) 
 * [**keras**](https://keras.io/api/)
@@ -21,4 +21,4 @@ To learn more about the dataset, checkout its [registry page](http://registry.ml
 After this lecture, you are encouraged to work on two other image classification datasets available on Radiant MLHub. 
 1) [SEN12-FLOOD](http://registry.mlhub.earth/10.21227/w6xz-s898/): This dataset contains imagery of Sentinel-2 and Sentinel-1 satellites with labels for presence of flood in the imagery.
 
-2) [BigEarthNet](http://registry.mlhub.earth/10.14279/depositonce-10149/): This is a land cover classification dataset, and it contains ~570,000 images with multiclass labels for each image. This is a very large dataset, and if you are running it on a local computer, you may need to select a subset of the data for training. 
+2) [BigEarthNet](http://registry.mlhub.earth/10.14279/depositonce-10149/): This is a land cover classification dataset, and it contains ~570,000 images with multiclass labels for each image. This is a very large dataset, and if you are running it on a local computer, you may need to select a subset of the data for training.