Bugfix: Fix duplicate definition error being thrown when running `db:sample`

Because we're now including `factory_girl_rails` in the bundled group for
development, test and staging, requiring the factories in `sample.rb` was
throwing a `DuplicateDefinitionError`.

I removed the lines from `sample.rb` which required `factory_girl` and also the
line which required the factory definitions.

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Change-Id:     I3773f8914a971d8f24f8dd12d02af135d9d7f6b8
Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>