its profile-formats, not profile-format, also add cache-formats for future use

(Portage version: 2.2.01.19572-prefix/git/Interix x86, unsigned Manifest commit)

metadata/layout.conf

@@ -14,4 +14,10 @@ update-changelog = true
 # the default *is* actually pms, but better safe then sorry
 # since we don't actually need stuff like package.* as
 # directory
-profile-format = pms
+profile-formats = pms
+
+# we are on git, so we can use a fancy cache format
+# when portage-2.1.10.29 was stable for a while.
+# it defaults to pms currently. (and we currently don't distribute
+# cache anyway)
+#cache-formats = md5-dict