test1540: Remove unused macro TEST_HANG_TIMEOUT

The macro has never been used, and it there is not really any place
where it would make sense to add timing checks.

Closes #2852

tests/libtest/lib1540.c

@@ -79,8 +79,6 @@ static size_t write_callback(void *ptr, size_t size, size_t nmemb, void *userp)
   return CURL_WRITEFUNC_PAUSE;
 }
 
-#define TEST_HANG_TIMEOUT 60 * 1000
-
 int test(char *URL)
 {
   CURL *curls = NULL;