Update release.md

Author: SethTisue

.github/ISSUE_TEMPLATE/release.md

@@ -116,6 +116,7 @@ Key links:
 ### Afterwards
 - [ ] Create PR to add/update spec links on scala-lang.org (example: https://github.com/scala/scala-lang/pull/1050)
 - [ ] Create PR to update `scala-version` on docs.scala-lang.org (example: https://github.com/scala/docs.scala-lang/pull/1294)
-- [ ] Create PR to update `versions.properties` (new file generated by the bootstrap job) and the `baseVersion` in `build.sbt` and the MiMa base version and exclusion filters and (on major version bump) `spec/_config.yml`
+- [ ] Create PR to update `versions.properties` (new file generated by the bootstrap job) and the `baseVersion` in `build.sbt` and the MiMa base version and exclusion filters and (if it's a major bump) `spec/_config.yml`
+- [ ] If it's a major bump, PR an update to `latestSpecVersion` in `spec/_config.yml` on the old branch, so that spec is marked as no longer current
 - [ ] Create PR to update https://github.com/lightbend/reactive-platform-docs/blob/master/src/main/paradox/supported-modules/index.md
 - [ ] Update [WhiteSource](https://github.com/lightbend/scala-team/wiki/Whitesource)