advapi32/tests: Write-strings warnings fix

[Andrew Talbot]

Changelog:
    advapi32/tests: Write-strings warnings fix.

diff -urN a/dlls/advapi32/tests/security.c b/dlls/advapi32/tests/security.c
--- a/dlls/advapi32/tests/security.c	2006-08-05 10:45:38.000000000 +0100
+++ b/dlls/advapi32/tests/security.c	2006-08-13 09:36:14.000000000 +0100
@@ -88,7 +88,7 @@
     hmod = GetModuleHandle("advapi32.dll");
 }
 
-static void test_str_sid(char *str_sid)
+static void test_str_sid(const char *str_sid)
 {
     PSID psid;
     char *temp;