tracetool: avoid invalid escape in Python string

This is an error in Python 3.12; fix it by using a raw string literal.

Cc:  <qemu-stable@nongnu.org>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20231108105649.60453-1-marcandre.lureau@redhat.com>

scripts/tracetool/__init__.py

@@ -91,7 +91,7 @@ def out(*lines, **kwargs):
 def validate_type(name):
     bits = name.split(" ")
     for bit in bits:
-        bit = re.sub("\*", "", bit)
+        bit = re.sub(r"\*", "", bit)
         if bit == "":
             continue
         if bit == "const":