Remove unnecessary cast in Quick Assist.

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

Index: pkg/analysis_server/lib/src/services/correction/assist_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
index 2034c5431992a63811702eaef18392abab0ec19c..4358dd38c260dc27a6bf7b095461ccd61c5e08b9 100644
--- a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
@@ -1130,11 +1130,9 @@ class AssistProcessor {
     }
     // returns
     if (thenStatement is ReturnStatement && elseStatement is ReturnStatement) {
-      ReturnStatement thenReturn = thenStatement as ReturnStatement;
-      ReturnStatement elseReturn = elseStatement as ReturnStatement;
       String conditionSrc = _getNodeText(ifStatement.condition);
-      String theSrc = _getNodeText(thenReturn.expression);
-      String elseSrc = _getNodeText(elseReturn.expression);
+      String theSrc = _getNodeText(thenStatement.expression);
+      String elseSrc = _getNodeText(elseStatement.expression);
       _addReplaceEdit(
           rangeNode(ifStatement),
           'return $conditionSrc ? $theSrc : $elseSrc;');