tests/tcg/aarch64: Fix test-mte.py

tests/tcg/aarch64: Fix test-mte.py

Python 3.12 warns:

  TEST    gdbstub MTE support on aarch64
/home/rth/qemu/src/tests/tcg/aarch64/gdbstub/test-mte.py:21: SyntaxWarning: invalid escape sequence '\('
  PATTERN_0 = "Memory tags for address 0x[0-9a-f]+ match \(0x[0-9a-f]+\)."

Double up the \ to pass one through to the pattern.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240719004143.1319260-1-richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>