PrintRecommendationService: Add an exported flag in manifest

With b/150232615, we will need an explicit value set for the exported
flag when intent filters are present, as the default behavior is
changing for S+. This change adds the value reflecting the previous
default to the manifest.

Bug: 150232615
Test: TH
Change-Id: I392c0982d0db69d2eddafcc616b5a9d7c14a6ae9