test quora: reduce checking

Because tsv file is too big(404,290 rows).

Before this change:

```bash
$ time ruby -I lib test/run-test.rb -t "/QuoraDuplicateQuestionPairTest/" -v
Loaded suite test
Started
QuoraDuplicateQuestionPairTest:
  test: #each:                                                         .: (17.476536)

Finished in 17.476912 seconds.
-------------------------------------------------------------------------------------
1 tests, 1 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
-------------------------------------------------------------------------------------
0.06 tests/s, 0.06 assertions/s

real    0m18.117s
user    0m17.554s
sys     0m0.383s
```

After this change:

$ time ruby -I lib test/run-test.rb -t "/QuoraDuplicateQuestionPairTest/" -v
Loaded suite test
Started
QuoraDuplicateQuestionPairTest:
  test: #each:                                                          .: (0.001124)

Finished in 0.001461 seconds.
-------------------------------------------------------------------------------------
1 tests, 1 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
-------------------------------------------------------------------------------------
684.46 tests/s, 684.46 assertions/s

real    0m0.595s
user    0m0.376s
sys     0m0.126s

Refs red-data-tools#188.

test/test-quora-duplicate-question-pair.rb

@@ -8,26 +8,13 @@ def record(*args)
   end
 
   test("#each") do
-    records = @dataset.each.to_a
-    assert_equal([
-                   404290,
-                   record(0,
-                          1,
-                          2,
-                          "What is the step by step guide to invest in share market in india?",
-                          "What is the step by step guide to invest in share market?",
-                          false),
-                   record(404289,
-                          537932,
-                          537933,
-                          "What is like to have sex with cousin?",
-                          "What is it like to have sex with your cousin?",
-                          false),
-                 ],
-                 [
-                   records.size,
-                   records.first,
-                   records.last,
-                 ])
+    records = @dataset.each
+    assert_equal(record(0,
+                        1,
+                        2,
+                        "What is the step by step guide to invest in share market in india?",
+                        "What is the step by step guide to invest in share market?",
+                        false),
+                 records.first)
   end
 end