test,lsudev: fix warnings with -Wsign-compare

lsudev.c: In function ‘println’:
  lsudev.c:64:19: error: comparison of integer expressions of different signedness: ‘int’ and ‘guint’ {aka ‘unsigned int’} [-Werror=sign-compare]
     64 |     for (i = 0; i < indent; i++)
        |                   ^

test/lsudev.c

@@ -55,7 +55,7 @@ println (guint indent, const char *fmt, ...)
 {
     va_list args;
     GString *output;
-    int i;
+    guint i;
 
     g_return_if_fail (fmt != NULL);
 
@@ -175,4 +175,3 @@ main (int argc, char *argv[])
 
     return 0;
 }
-