Update doc comments to follow style guide.

sdk/lib/_internal/pub/lib/src/exit_codes.dart

Index: sdk/lib/_internal/pub/lib/src/exit_codes.dart
diff --git a/sdk/lib/_internal/pub/lib/src/exit_codes.dart b/sdk/lib/_internal/pub/lib/src/exit_codes.dart
index a1683cd9c6b7784974c6872f96874af0fc5d4b91..ebe8e8deab8e584eb14f1a8156bb00fa404634ce 100644
--- a/sdk/lib/_internal/pub/lib/src/exit_codes.dart
+++ b/sdk/lib/_internal/pub/lib/src/exit_codes.dart
@@ -2,9 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// Exit code constants. From [the BSD sysexits manpage][manpage]. Not every
-/// constant here is used, even though some of the unused ones may be
-/// appropriate for errors encountered by pub.
+/// Exit code constants.
+///
+/// From [the BSD sysexits manpage][manpage]. Not every constant here is used,
+/// even though some of the unused ones may be appropriate for errors
+/// encountered by pub.
 ///
 /// [manpage]: http://www.freebsd.org/cgi/man.cgi?query=sysexits
 library pub.exit_codes;