docs(roadmap): name 0.7.9 as the current release (#2623)

ROADMAP.md's released section moves from 0.7.8 to 0.7.9: the heading, the release link, and the published 0.7.9 notes' first two sentences with "OpenRig 0.7.9" written as "it", as the 0.7.8 update did. The pointer to the release notes for what shipped, known issues, upgrade instructions and contributor credits is unchanged. Text only.

ROADMAP.md

@@ -6,9 +6,9 @@ This isn't a schedule or a promise: we release often, and an item ships when a g
 To see what's being worked on, by release and theme, open the [OpenRig roadmap board](https://github.com/users/mvschwarz/projects/1).
 Issues labelled `good first issue` are also listed on the [contribute page](https://github.com/mvschwarz/openrig/contribute).
 
-## Released in 0.7.8
+## Released in 0.7.9
 
-[0.7.8 is published](https://github.com/mvschwarz/openrig/releases/tag/v0.7.8): it lets a person answer a runner seat's permission requests, with a conformance check and an example runner to build against. See its release notes for what shipped, known issues, upgrade instructions and contributor credits.
+[0.7.9 is published](https://github.com/mvschwarz/openrig/releases/tag/v0.7.9): it follows through on 0.7.8. A person's typed words on a runner seat's permission ask now reach the agent, each permit OpenRig grants a runner by default is recorded, and a runner can keep a long, quiet turn reading working. See its release notes for what shipped, known issues, upgrade instructions and contributor credits.
 
 ## How to help