BUILD: debug: remove leftover parentheses in ABORT_NOW()

BUILD: debug: remove leftover parentheses in ABORT_NOW()

Since d480b7b ("MINOR: debug: make ABORT_NOW() store the caller's line
number when using abort"), building with 'DEBUG_USE_ABORT' fails with:

  |In file included from include/haproxy/api.h:35,
  |                 from include/haproxy/activity.h:26,
  |                 from src/ev_poll.c:20:
  |include/haproxy/thread.h: In function â\80\98ha_set_threadâ\80\99:
  |include/haproxy/bug.h:107:47: error: expected â\80\98;â\80\99 before â\80\98_with_lineâ\80\99
  |  107 | #define ABORT_NOW() do { DUMP_TRACE(); abort()_with_line(__LINE__); } while (0)
  |      |                                               ^~~~~~~~~~
  |include/haproxy/bug.h:129:25: note: in expansion of macro â\80\98ABORT_NOWâ\80\99
  |  129 |                         ABORT_NOW();                                    \
  |      |                         ^~~~~~~~~
  |include/haproxy/bug.h:123:9: note: in expansion of macro â\80\98__BUG_ONâ\80\99
  |  123 |         __BUG_ON(cond, file, line, crash, pfx, sfx)
  |      |         ^~~~~~~~
  |include/haproxy/bug.h:174:30: note: in expansion of macro â\80\98_BUG_ONâ\80\99
  |  174 | #  define BUG_ON(cond)       _BUG_ON     (cond, __FILE__, __LINE__, 3, "FATAL: bug ",     "")
  |      |                              ^~~~~~~
  |include/haproxy/thread.h:201:17: note: in expansion of macro â\80\98BUG_ONâ\80\99
  |  201 |                 BUG_ON(!thr->ltid_bit);
  |      |                 ^~~~~~
  |compilation terminated due to -Wfatal-errors.
  |make: *** [Makefile:1006: src/ev_poll.o] Error 1

This is because of a leftover: abort()_with_line(__LINE__);
                                    ^^
Fixing it by removing the extra parentheses after 'abort' since the
abort() call is now performed under abort_with_line() helper function.

This was raised by Ilya in GH #2440.

No backport is needed, unless the above commit gets backported.

(cherry picked from commit be0165b24951f68e63b327179babebed399f62ee)
Signed-off-by: Willy Tarreau <w@1wt.eu>