Fix msec documentation description typo

doc/classes/OS.xml

@@ -54,7 +54,7 @@
 			<argument index="0" name="msec" type="int">
 			</argument>
 			<description>
-				Delay execution of the current thread by [code]msec[/code] milliseconds. [code]usec[/code] must be greater than or equal to [code]0[/code]. Otherwise, [method delay_msec] will do nothing and will print an error message.
+				Delay execution of the current thread by [code]msec[/code] milliseconds. [code]msec[/code] must be greater than or equal to [code]0[/code]. Otherwise, [method delay_msec] will do nothing and will print an error message.
 			</description>
 		</method>
 		<method name="delay_usec" qualifiers="const">