Remove unused Structure.taskToKey

buildfile/src/main/scala/sbt/internal/EvaluateConfigurations.scala

@@ -351,17 +351,6 @@ object BuildUtilLite:
 end BuildUtilLite
 
 object Index {
-  def taskToKeyMap(data: Settings[Scope]): Map[Task[?], ScopedKey[Task[?]]] = {
-
-    val pairs = data.scopes flatMap (scope =>
-      data.data(scope).entries collect { case AttributeEntry(key, value: Task[_]) =>
-        (value, ScopedKey(scope, key.asInstanceOf[AttributeKey[Task[?]]]))
-      }
-    )
-
-    pairs.toMap[Task[?], ScopedKey[Task[?]]]
-  }
-
   def allKeys(settings: Seq[Setting[?]]): Set[ScopedKey[?]] = {
     val result = new java.util.HashSet[ScopedKey[?]]
     settings.foreach { s =>

main/src/main/scala/sbt/internal/BuildStructure.scala

@@ -71,7 +71,6 @@ final class BuildStructure(
 // information that is not original, but can be reconstructed from the rest of BuildStructure
 final class StructureIndex(
     val keyMap: Map[String, AttributeKey[?]],
-    val taskToKey: Map[Task[?], ScopedKey[Task[?]]],
     val triggers: Triggers,
     val keyIndex: KeyIndex,
     val aggregateKeyIndex: KeyIndex,

main/src/main/scala/sbt/internal/Load.scala

@@ -384,7 +384,6 @@ private[sbt] object Load {
     val aggIndex = KeyIndex.aggregate(scopedKeys.toVector, extra(keyIndex), projectsMap, configsMap)
     new StructureIndex(
       Index.stringToKeyMap(attributeKeys),
-      Index.taskToKeyMap(data),
       Index.triggers(data),
       keyIndex,
       aggIndex