remove JRuby PostgreSQL from allow_failures of .travis.yml

Tests pass on Travis.
* jruby 1.7.9 (1.9.3p392) 2014-01-09 87b108a on Java HotSpot(TM) 64-Bit Server VM 1.7.0_45-b18 [linux-amd64]
* jdbc-postgres (9.3.1100)
* activerecord-jdbc-adapter (1.3.5)
* activerecord-jdbcpostgresql-adapter (1.3.5)

--HG--
extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012668