Update to sbt 2.0.0-M4 and Scala 3.6.4, resolve new warnings.

Author: mrdziuban

sbt-plugin/build.sbt

@@ -22,7 +22,7 @@ inThisBuild(
 )
 
 val scala2 = "2.12.20"
-val scala3 = "3.6.3"
+val scala3 = "3.6.4"
 
 val `sbt-github-dependency-submission` = project
   .in(file("."))
@@ -32,7 +32,7 @@ val `sbt-github-dependency-submission` = project
     pluginCrossBuild / sbtVersion := {
       scalaBinaryVersion.value match {
         case "2.12" => "1.5.8"
-        case _      => "2.0.0-M3"
+        case _      => "2.0.0-M4"
       }
     },
     scalaVersion := scala2,

sbt-plugin/src/main/scala/ch/epfl/scala/AnalyzeDependencyGraph.scala

@@ -205,7 +205,7 @@ object AnalyzeDependencyGraph {
               firstPatchedVersion,
               securityVulnerability.collectFirst { case JField("severity", JString(sev)) => sev }.get
             )
-        }
+        }.toSeq
       case _ =>
         val message =
           s"Unexpected status ${httpResp.status} ${httpResp.statusText} with body:\n${httpResp.bodyAsString}"

sbt-plugin/src/main/scala/ch/epfl/scala/GithubDependencyGraphPlugin.scala

@@ -183,12 +183,11 @@ object GithubDependencyGraphPlugin extends AutoPlugin {
             allDependencies += (getReference(caller.caller) -> moduleRef)
         }
 
-        val allDependenciesMap: Map[String, Vector[String]] = allDependencies.view
-          .groupBy(_._1)
-          .mapValues {
-            _.map { case (_, dep) => dep }.toVector
+        val allDependenciesMap: Map[String, Vector[String]] =
+          allDependencies.foldLeft(Map.empty[String, Vector[String]]) {
+            case (acc, (ref, dep)) =>
+              acc + (ref -> (acc.getOrElse(ref, Vector.empty) :+ dep))
           }
-          .toMap
         val allDirectDependenciesRefs: Set[String] = allDirectDependencies.map(getReference).toSet
 
         val resolved =