Fix lazy import in Plasma docs

91d299e removed the deprecated wrapper for lazy but the Plasma docs
still referred to it.

libqtile/layout/plasma.py

@@ -753,8 +753,8 @@ class Plasma(Layout):
 
     .. code:: python
 
-        from libqtile.command import lazy
         from libqtile.config import EzKey
+        from libqtile.lazy import lazy
         ...
         keymap = {
             'M-h': lazy.layout.left(),