deps: update to libpathrs v0.2.5

This update includes a few breaking API changes that I needed to get in
before an actual runc release depends on it, so that we don't need to
deal with compatibility shims for them (or bumping the SOVERSION).

From a Go API perspective, there were no major changes -- though this
bump did also require a bump to github.com/cyphar/filepath-securejoin
because one of the wrapped APIs changed from int to uint64 as a flag
argument type. Again, better to get this done before we really depend on
this in a public way.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

vendor/github.com/cyphar/filepath-securejoin/VERSION

@@ -1 +1 @@
-0.6.1
+0.7.0