docs/esp8266/tutorial: Fix typo, "its" to "it's" in powerctrl.rst.

mattdbr · dpgeorge · commit d003daee06d0 · 2017-07-24T10:33:03.000+10:00
diff --git a/docs/esp8266/tutorial/powerctrl.rst b/docs/esp8266/tutorial/powerctrl.rst
@@ -22,7 +22,7 @@ processing power, at the expense of current consumption::
     160000000
 
 You can change to the higher frequency just while your code does the heavy
-processing and then change back when its finished.
+processing and then change back when it's finished.
 
 Deep-sleep mode
 ---------------
