qemu-options.hx: remove stray quote

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230202223121.252073-1-jsnow@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

qemu-options.hx

@@ -1606,7 +1606,7 @@ SRST
 
     .. parsed-literal::
 
-        |qemu_system_x86| -drive file=a -drive file=b"
+        |qemu_system_x86| -drive file=a -drive file=b
 
     is interpreted like: