Remove MatplotlibDeprecationWarning in Matplotlib Lecture (#289)

* remove MatplotlibDeprecationWarning

* update false-positive link

Author: HumphreyYang

lectures/_config.yml

@@ -20,7 +20,8 @@ sphinx:
     # false-positive links
     linkcheck_ignore: ['https://github.com/matplotlib/matplotlib/blob/v3.6.2/lib/matplotlib/axes/_axes.py#L1417-L1669',
                        'https://ieeexplore.ieee.org/document/8757088',
-                       'https://www.sciencedirect.com/science/article/pii/S1477388021000177']
+                       'https://www.sciencedirect.com/science/article/pii/S1477388021000177',
+                       'https://keras.io/']
     html_favicon: _static/lectures-favicon.ico
     html_theme: quantecon_book_theme
     html_static_path: ['_static']

lectures/matplotlib.md

@@ -319,7 +319,8 @@ def draw_graphs(style='default'):
         # and a line graph with random Y values
         axes[3].plot(x, rnormY, linewidth=2, alpha=0.7)
 
-    plt.suptitle(f'Style: {style}', fontsize=13)
+    style_name = style.split('-')[0]
+    plt.suptitle(f'Style: {style_name}', fontsize=13)
     plt.show()
 
 ```
@@ -329,7 +330,7 @@ Let's see what some of the styles look like.
 First, we draw graphs with the style sheet `seaborn`
 
 ```{code-cell} python3
-draw_graphs(style='seaborn')
+draw_graphs(style='seaborn-v0_8')
 ```
 
 We can use `grayscale` to remove colors in plots