readline/search.c: Remove useless parameter '0' for rl_message()

readline/search.c: Remove useless parameter '0' for rl_message()

The related warning under Darwin x86_64:

  gcc -c -DHAVE_CONFIG_H    -I. -I../../binutils-gdb/readline -DRL_LIBRARY_VERSION='"6.2"' -g -O2 ../../binutils-gdb/readline/search.c
  ../../binutils-gdb/readline/search.c:213:24: warning: data argument not used by format string [-Wformat-extra-args]
    rl_message ("%s", p, 0);
                ~~~~     ^
  1 warning generated.

readline/ChangeLog.gdb:

	* search.c (_rl_nsearch_init): Remove useless parameter '0' for
	rl_message().

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>