modular_test: prepare for curly_braces lint change

This aligns this code better with Effective Dart and prepares for the
upcoming lint rule change at https://dart-review.googlesource.com/c/sdk/+/353140.

Change-Id: Ibfb4736ae01a6e2d843f9faf19eba08c16ff6c92
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/353222
Reviewed-by: Joshua Litt <joshualitt@google.com>
Commit-Queue: Joshua Litt <joshualitt@google.com>
Auto-Submit: Samuel Rawlins <srawlins@google.com>
diff --git a/pkg/modular_test/lib/src/pipeline.dart b/pkg/modular_test/lib/src/pipeline.dart
index 1c2ddf9..9c04225 100644
--- a/pkg/modular_test/lib/src/pipeline.dart
+++ b/pkg/modular_test/lib/src/pipeline.dart
@@ -158,7 +158,9 @@
 
     if ((step.onlyOnMain && !module.isMain) ||
         (step.onlyOnSdk && !module.isSdk) ||
-        (step.notOnSdk && module.isSdk)) return;
+        (step.notOnSdk && module.isSdk)) {
+      return;
+    }
     // Include only requested data from transitive dependencies.
     Map<Module, Set<DataId>> visibleData = {};