Update scalafmt-core to 3.9.1

Author: scala-steward-bot

.scalafmt.conf

@@ -9,7 +9,7 @@ docstrings.style = keep
 includeCurlyBraceInSelectChains = false
 optIn.breakChainOnFirstMethodDot = false
 trailingCommas = preserve
-version = "3.9.0"
+version = "3.9.1"
 project.layout = StandardConvention
 rewrite.scala3.convertToNewSyntax = true
 fileOverride {