msi/tests: Write-strings warning fix

[Andrew Talbot]

Changelog:
    msi/tests: Write-strings warning fix.

diff -urN a/dlls/msi/tests/install.c b/dlls/msi/tests/install.c
--- a/dlls/msi/tests/install.c	2006-07-27 17:27:19.000000000 +0100
+++ b/dlls/msi/tests/install.c	2006-07-27 19:53:26.000000000 +0100
@@ -694,7 +694,7 @@
 {
     MSIHANDLE hdb, view, rec;
     char path[MAX_PATH];
-    LPSTR query;
+    LPCSTR query;
     UINT r, count;
 
     CoInitialize(NULL);