Fix formatting and typo in MapSourceToResponseEvent

Author: benjie

.github/algorithm-format-check.mjs

@@ -100,7 +100,7 @@ for (const filename of filenames) {
           console.dir(line);
           console.dir(nextLine);
           console.log();
-          // TODO: process.exitCode = 1;
+          process.exitCode = 1;
         }
       }
     }

spec/Section 6 -- Execution.md

@@ -290,11 +290,11 @@ subscription selection set using that event as a root value.
 MapSourceToResponseEvent(sourceStream, subscription, schema, variableValues):
 
 - Return a new event stream {responseStream} which yields events as follows:
-- For each {event} on {sourceStream}:
-  - Let {response} be the result of running
-    {ExecuteSubscriptionEvent(subscription, schema, variableValues, event)}.
-  - Yield an event containing {response}.
-- When {responseStream} completes: complete this event stream.
+  - For each {event} on {sourceStream}:
+    - Let {response} be the result of running
+      {ExecuteSubscriptionEvent(subscription, schema, variableValues, event)}.
+    - Yield an event containing {response}.
+  - When {sourceStream} completes: complete {responseStream}.
 
 ExecuteSubscriptionEvent(subscription, schema, variableValues, initialValue):