ci: release-please manifest update version (#386)

@vicwomg Trying to get the right version in release please by pinning it
to 1.3.0. If it doesn't work we can bootstrap it.

I see you do merge commits when merging PR's. It would be better to
rebase on main. That gives you a much more tidy history and it won't
confuse release-please.

.release-please-manifest.json

@@ -1,3 +1 @@
-{
-
-}
+{".":"1.3.0"}