Remove TestLDAResults.test_expElogbeta()

This test was using unexposed internal class methods in a way which was
incompatible with legitimate usage. It worked before due to how the
internals of the class were desiged, but no longer due to the fact that
the LDAResults._expElogbeta() method is const.

rosetta/tests/test_text.py

@@ -323,16 +323,6 @@ def test_dirichlet_expectation(self):
             [-0.13470677,  -13.32429878]]).T
         assert_allclose(result, benchmark, atol=1e-4)
 
-    def test_expElogbeta(self):
-        # Make sure equal to exponential of dirichlet_expectation when we
-        # pass in all ones
-        lda = self.choose_lda('lda')
-        lda._lambda_word_sums = pd.Series(
-            np.ones(lda.num_topics), index=lda.topics)
-        result = lda._expElogbeta
-        benchmark = np.exp(lda._dirichlet_expectation(lda.pr_token_topic))
-        assert_frame_equal(result, benchmark)
-
     def test_predict_1(self):
         # Use fact that w0  <--> topic_0,  w1 <--> topic_1
         lda = self.choose_lda('lda_2')