Revert "bump up rack version to the one that includes the Hash DoS fix"

Rack 1.1.3 also changes the Set-Cookie header to expects a
newline-delimited string instead of an Array, which breaks Rails 2.3's
expectations in a variety of ways.

This reverts commit 27a508c91e04b619c8a1eb50ef115b226b21182c.

Conflicts:
	actionpack/Rakefile