Update scalafmt-core to 3.8.4

Author: scala-steward-bot

.scalafmt.conf

@@ -6,7 +6,7 @@ docstrings.style = keep
 align.openParenCallSite = false
 includeCurlyBraceInSelectChains = false
 optIn.breakChainOnFirstMethodDot = false
-version = "3.8.3"
+version = "3.8.4"
 runner.dialect = Scala3
 rewrite.scala3.convertToNewSyntax = true
 rewrite.scala3.newSyntax.control = false