[thread.sharedtimedmutex.class] formatting not consistent with similar cases

[zygoloid]

DIS 14882:2014 NB comment JP 14:

In 30.4.1.4.1:

Formatting for class shared_timed_mutex is not compatible with others.
In addition, at lock() function line, there is a comment, “//blocking”, but in the similar class, timed_mutex, there’s no comment for lock() function. They should be uniformed.

Proposed change:

Remove a blank line under “namespace std{“.
Indent whole class definition by 2 columns.
Remove the comment at lock() and lock_shared().
(or add the same comment at timed_mutex::lock() )