doc: console is asynchronous unless it's a file

Mea culpa, looks like I forgot to update console.markdown in commit
dac1d38 ("doc: stdout/stderr can block when directed to file").
This commit rectifies that.

Refs: https://github.com/nodejs/node/issues/5131
PR-URL: https://github.com/nodejs/node/pull/5133
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Evan Lucas <evanlucas@me.com>

doc/api/console.markdown

@@ -53,19 +53,10 @@ duplicate the browsers functionality exactly.
 
 ## Asynchronous vs Synchronous Consoles
 
-The console functions are synchronous when the destination is a terminal or
+The console functions are asynchronous unless the destination is a file.
-a file (to avoid lost messages in case of premature exit) and asynchronous
+Disks are fast and operating systems normally employ write-back caching;
-when the destination is a pipe (to avoid blocking for long periods of time).
+it should be a very rare occurrence indeed that a write blocks, but it
-
+is possible.
-In the following example, stdout is non-blocking while stderr is blocking:
-
-```
-$ node script.js 2> error.log | tee info.log
-```
-
-Typically, the distinction between blocking/non-blocking is not important
-unless an application is logging significant amounts of data. High volume
-logging *should* use a `Console` instance that writes to a pipe.
 
 ## Class: Console