Rails4: replace hard-coded html with class at ApplicationHelperTest#test_redmine_links_with_a_different_project_before_current_project

See r12784 comment.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012806
use escaped "Can't" constant at ApplicationHelperTest

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012807