docs(api): unify selector references to include xpath (#1150)

Author: arjunattam

docs/api.md

@@ -1480,8 +1480,7 @@ This is a shortcut for [page.mainFrame().url()](#frameurl)
 - returns: <[Promise]<[JSHandle]>> Promise which resolves to a JSHandle of the success value
 
 This method behaves differently with respect to the type of the first parameter:
-- if `selectorOrFunctionOrTimeout` is a `string`, then the first argument is treated as a [selector] or [xpath], depending on whether or not it starts with '//', and the method is a shortcut for
-  [page.waitForSelector](#pagewaitforselectorselector-options)
+- if `selectorOrFunctionOrTimeout` is a `string`, then the first argument is treated as a [selector] and the method is a shortcut for [page.waitForSelector](#pagewaitforselectorselector-options)
 - if `selectorOrFunctionOrTimeout` is a `function`, then the first argument is treated as a predicate to wait for and the method is a shortcut for [page.waitForFunction()](#pagewaitforfunctionpagefunction-options-args).
 - if `selectorOrFunctionOrTimeout` is a `number`, then the first argument is treated as a timeout in milliseconds and the method returns a promise which resolves after the timeout
 - otherwise, an exception is thrown
@@ -2135,8 +2134,7 @@ Returns frame's url.
 - returns: <[Promise]<[JSHandle]>> Promise which resolves to a JSHandle of the success value
 
 This method behaves differently with respect to the type of the first parameter:
-- if `selectorOrFunctionOrTimeout` is a `string`, then the first argument is treated as a [selector] or [xpath], depending on whether or not it starts with '//', and the method is a shortcut for
-  [frame.waitForSelector](#framewaitforselectorselector-options)
+- if `selectorOrFunctionOrTimeout` is a `string`, then the first argument is treated as a [selector] and the method is a shortcut for [frame.waitForSelector](#framewaitforselectorselector-options)
 - if `selectorOrFunctionOrTimeout` is a `function`, then the first argument is treated as a predicate to wait for and the method is a shortcut for [frame.waitForFunction()](#framewaitforfunctionpagefunction-options-args).
 - if `selectorOrFunctionOrTimeout` is a `number`, then the first argument is treated as a timeout in milliseconds and the method returns a promise which resolves after the timeout
 - otherwise, an exception is thrown