Fix documentation of a recent change

* src/fns.c (Fyes_or_no_p): Don't use braces around one-line
block.
(syms_of_fns) <use-short-answers>: Improve the wording of the doc
string.
* etc/NEWS: Improve wording of the entry about 'use-short-answers'.

etc/NEWS

@@ -2416,8 +2416,9 @@ use the function 'read-key' to read a character instead of using the minibuffer.
 
 ---
 ** New variable 'use-short-answers' to use 'y-or-n-p' instead of 'yes-or-no-p'.
-This relieves of the need to define an alias that maps one to another
-in the init file.  The same variable also affects the function 'read-answer'.
+This eliminates the need to define an alias that maps one to another
+in the init file.  The same variable also controls whether the
+function 'read-answer' accepts short answers.
 
 +++
 ** 'set-window-configuration' now takes an optional 'dont-set-frame'

src/fns.c

@@ -2874,9 +2874,7 @@ if `last-nonmenu-event' is nil, and `use-dialog-box' is non-nil.  */)
     }
 
   if (use_short_answers)
-    {
-      return call1 (intern ("y-or-n-p"), prompt);
-    }
+    return call1 (intern ("y-or-n-p"), prompt);
 
   AUTO_STRING (yes_or_no, "(yes or no) ");
   prompt = CALLN (Fconcat, prompt, yes_or_no);
@@ -5911,10 +5909,10 @@ this variable.  */);
 
   DEFVAR_BOOL ("use-short-answers", use_short_answers,
     doc: /* Non-nil means `yes-or-no-p' uses shorter answers "y" or "n".
-It's discouraged to use single-key answers because `yes-or-no-p' is
-intended to be used when it's thought that you should not respond too
-quickly, so you take time and perhaps think more about the answer.
-When non-nil, then `yes-or-no-p' uses `y-or-n-p' to read an answer.
+When non-nil, `yes-or-no-p' will use `y-or-n-p' to read the answer.
+We recommend against setting this variable non-nil, because `yes-or-no-p'
+is intended to be used when users are expected not to respond too
+quickly, but to take their time and perhaps think about the answer.
 The same variable also affects the function `read-answer'.  */);
   use_short_answers = false;