Run swift-format

Author: mbrandonw

Sources/ConcurrencyExtras/MainSerialExecutor.swift

@@ -17,7 +17,7 @@
   ///
   /// See <doc:ReliablyTestingAsync> for more information on why this tool is needed to test
   /// async code and how to use it.
-  /// 
+  ///
   /// > Warning: This API is only intended to be used from tests to make them more reliable. Please do
   /// > not use it from application code.
   /// >