vmstat: Add NEWS and revert comment from prev

Reverted the translation hint as the fields are used for both
normal and wide modes, so need to fit the smaller of the two.

Added NEWS item

References:
 commit 01c1b2345e

vmstat.c

@@ -260,9 +260,9 @@ static void new_header(void)
 
     printf(
         w_option ? wide_format : format,
-        /* Translation Hint: max 4 chars */
+        /* Translation Hint: max 2 chars */
          _("r"),
-        /* Translation Hint: max 4 chars */
+        /* Translation Hint: max 2 chars */
          _("b"),
         /* Translation Hint: max 6 chars */
          _("swpd"),