Update scalafmt-core to 3.8.4 (#677)

Co-authored-by: eikek-scala-steward <[email protected]>

Author: eikek-scala-steward[bot]

.scalafmt.conf

@@ -1,4 +1,4 @@
-version = "3.8.2"
+version = "3.8.4"
 
 preset = default
 align.preset = some