Remove the old task model

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index eba635ff26ffc439c35e353eef55e1e949635319..eb6e2537f5821010cd0cfea09121fd66d333aa49 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -450,11 +450,7 @@ class FixProcessor {
       PartDirective directive = node.parent;
       Source partSource = directive.source;
       CompilationUnit partUnit;
-      if (AnalysisEngine.instance.useTaskModel) {
-        partUnit = context.getResolvedCompilationUnit2(partSource, partSource);
-      } else {
-        partUnit = context.getResolvedCompilationUnit2(partSource, unitSource);
-      }
+      partUnit = context.getResolvedCompilationUnit2(partSource, partSource);
       if (partUnit != null) {
         CorrectionUtils partUtils = new CorrectionUtils(partUnit);
         CorrectionUtils_InsertDesc desc = partUtils.getInsertDescTop();