Updates newsboat: d7b8edc Feat: config: show how to specify locally-stored OPML files

diff --git a/modules/newsboat b/modules/newsboat
index ccf4f21f00e1dc506dbffef823930d37080ab839..d7b8edcf289a411968fa96f23273bfbd57f06a35 160000 (submodule)
--- a/modules/newsboat
+++ b/modules/newsboat
@@ -1 +1 @@
-Subproject commit ccf4f21f00e1dc506dbffef823930d37080ab839
+Subproject commit d7b8edcf289a411968fa96f23273bfbd57f06a35