Use classic style in old what's new entries (matplotlib#25623)

* whatsnew 0.99 rendered with classic style

* whatsnew 1.1 rendered with classic style

* whatsnew 1.2 rendered with classic style

Author: haojunsong-08

doc/users/prev_whats_new/whats_new_0.99.rst

@@ -33,6 +33,9 @@ installs).  See :ref:`mplot3d-examples-index` and
     from matplotlib import cm
     from mpl_toolkits.mplot3d import Axes3D
 
+
+    plt.style.use('classic')
+
     X = np.arange(-5, 5, 0.25)
     Y = np.arange(-5, 5, 0.25)
     X, Y = np.meshgrid(X, Y)
@@ -92,6 +95,9 @@ new mpl installs.   See :ref:`axes_grid1-examples-index`,
 
 
     fig = plt.figure()
+
+    plt.style.use('classic')
+
     ax = RGBAxes(fig, [0.1, 0.1, 0.8, 0.8])
 
     r, g, b = get_rgb()
@@ -139,6 +145,8 @@ well as "detach" the spine to offset it away from the data.  See
 
     fig = plt.figure()
 
+    plt.style.use('classic')
+
     x = np.linspace(0, 2*np.pi, 100)
     y = 2*np.sin(x)
 

doc/users/prev_whats_new/whats_new_1.1.rst

@@ -58,6 +58,8 @@ to address the most common layout issues.
 
 .. plot::
 
+    plt.style.use('classic')
+
     plt.rcParams['savefig.facecolor'] = "0.8"
     plt.rcParams['figure.figsize'] = 4, 3
 

doc/users/prev_whats_new/whats_new_1.2.rst

@@ -78,6 +78,8 @@ minimum and maximum colorbar extensions.
 
     import matplotlib.pyplot as plt
     import numpy as np
+    
+    plt.style.use('classic')
 
     x = y = np.linspace(0., 2*np.pi, 100)
     X, Y = np.meshgrid(x, y)