Grouped PRs don't respect previously closed PRs

[kubukoz]

Given the following build:

val root = project.in(file("."))
  .settings(
    scalaVersion := "2.12.20"
  )

And this repo config:

pullRequests.grouping = [
  { name = "scala", title = "Scala version updates", filter = [{group = "org.scala-lang", artifactId = "scala-library"}]},
  { name = "all", "title" = "Dependency updates", "filter" = [{"group" = "*"}] }
]

Running Steward once opened a PR to bump Scala to 2.13.16: https://github.com/kubukoz/steward-grouping-reopen-issue/pull/1

I closed it and ran Steward again. It opened an identical PR: https://github.com/kubukoz/steward-grouping-reopen-issue/pull/2

If I remember correctly, without grouping Steward would find that the update has already been issued and wouldn't attempt to do it again. Should this behavior be replicated when grouping is used?