`_auth_and_persist_outliers`: drop events we have already seen (#11994)

We already have two copies of this code, in 2/3 of the callers of
`_auth_and_persist_outliers`. Before I add a third, let's push it down.

1 files changed, 1 insertions, 0 deletions

diff --git a/changelog.d/11994.misc b/changelog.d/11994.misc
new file mode 100644
index 0000000000..d64297dd78
--- /dev/null
+++ b/changelog.d/11994.misc
@@ -0,0 +1 @@
+Move common deduplication code down into `_auth_and_persist_outliers`.