pyplot: do not apply kwargs twice in to x/yticklabels

If labels are given, `ax.set_xticklabels` is already passed the kwargs,
so a subsequent `label.update(kwargs)` is not necessary.

lib/matplotlib/pyplot.py

@@ -1797,10 +1797,10 @@ def xticks(ticks=None, labels=None, **kwargs):
 
     if labels is None:
         labels = ax.get_xticklabels()
+        for l in labels:
+            l.update(kwargs)
     else:
         labels = ax.set_xticklabels(labels, **kwargs)
-    for l in labels:
-        l.update(kwargs)
 
     return locs, labels
 
@@ -1857,10 +1857,10 @@ def yticks(ticks=None, labels=None, **kwargs):
 
     if labels is None:
         labels = ax.get_yticklabels()
+        for l in labels:
+            l.update(kwargs)
     else:
         labels = ax.set_yticklabels(labels, **kwargs)
-    for l in labels:
-        l.update(kwargs)
 
     return locs, labels