cleanup: add a missing license

Signed-off-by: Andrea Terzolo <[email protected]>

userspace/libsinsp/test/filterchecks/fspath.cpp

@@ -1,3 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0
+/*
+Copyright (C) 2024 The Falco Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 #include <test/helpers/threads_helpers.h>
 
 constexpr const char *name = "/tmp/random/dir...///../../name/";