Update logback-classic, logback-core to 1.5.21

Author: gu-scala-steward-public-repos[bot]

build.sbt

@@ -51,7 +51,7 @@ val simpleConfigurationVersion: String = "1.5.7"
 val googleOAuthClient: String = "1.39.0"
 val nettyVersion: String = "4.2.2.Final"
 val slf4jVersion: String = "1.7.36"
-val logbackVersion: String = "1.5.18"
+val logbackVersion: String = "1.5.21"
 
 val standardSettings = Seq[Setting[_]](
   // We should remove this when all transitive dependencies use the same version of scala-xml