Migrate Maniphest task blockers to modern EdgeType classes

Summary:
Prevents "edited tasks, added: 1; removed: 1"

Fixes T6757, using D9839 as an example

Test Plan: Added and removed blockers to/from tasks, saw the expected history entries.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T6757

Differential Revision: https://secure.phabricator.com/D11045

resources/sql/patches/migrate-maniphest-dependencies.php

@@ -18,7 +18,7 @@ foreach (new LiskMigrationIterator($table) as $task) {
   foreach ($deps as $dep) {
     $editor->addEdge(
       $task->getPHID(),
-      PhabricatorEdgeConfig::TYPE_TASK_DEPENDS_ON_TASK,
+      ManiphestTaskDependsOnTaskEdgeType::EDGECONST,
       $dep);
   }
   $editor->save();