shlwapi: Fix compiler warnings with flag -Wcast-qual.

dlls/shlwapi/url.c

@@ -278,7 +278,8 @@ HRESULT WINAPI UrlCanonicalizeW(LPCWSTR pszUrl, LPWSTR pszCanonicalized,
 {
     HRESULT hr = S_OK;
     DWORD EscapeFlags;
-    LPWSTR lpszUrlCpy, wk1, wk2, mp, mp2, root;
+    LPCWSTR wk1, root;
+    LPWSTR lpszUrlCpy, wk2, mp, mp2;
     INT state;
     DWORD nByteLen, nLen, nWkLen;
     WCHAR slash = '/';
@@ -322,7 +323,7 @@ HRESULT WINAPI UrlCanonicalizeW(LPCWSTR pszUrl, LPWSTR pszCanonicalized,
      *         6   have location (found /) save root location
      */
 
-    wk1 = (LPWSTR)pszUrl;
+    wk1 = pszUrl;
     wk2 = lpszUrlCpy;
     state = 0;