Fix tests for allowing duplicates in extract_links

tests/sample_data/link_extractor/linkextractor.html

@@ -13,6 +13,7 @@
       </div>
       <a href='http://example.com/sample3.html' title='sample 3'>sample 3 text</a>
       <a href='sample3.html'>sample 3 repetition</a>
+      <a href='sample3.html'>sample 3 repetition</a>
       <a href='sample3.html#foo'>sample 3 repetition with fragment</a>
       <a href='http://www.google.com/something'></a>
       <a href='http://example.com/innertag.html'><strong>inner</strong> tag</a>

tests/test_http_response.py

@@ -541,6 +541,7 @@ class TextResponseTest(BaseResponseTest):
             'http://example.com/sample2.html',
             'http://example.com/sample3.html',
             'http://example.com/sample3.html',
+            'http://example.com/sample3.html',
             'http://example.com/sample3.html#foo',
             'http://www.google.com/something',
             'http://example.com/innertag.html'

tests/test_linkextractors.py

@@ -53,6 +53,7 @@ class Base:
                 Link(url='http://example.com/sample2.html', text='sample 2'),
                 Link(url='http://example.com/sample3.html', text='sample 3 text'),
                 Link(url='http://example.com/sample3.html', text='sample 3 repetition'),
+                Link(url='http://example.com/sample3.html', text='sample 3 repetition'),
                 Link(url='http://example.com/sample3.html#foo', text='sample 3 repetition with fragment')
             ])
 
@@ -64,6 +65,7 @@ class Base:
                 Link(url='http://example.com/sample2.html', text='sample 2'),
                 Link(url='http://example.com/sample3.html', text='sample 3 text'),
                 Link(url='http://example.com/sample3.html', text='sample 3 repetition'),
+                Link(url='http://example.com/sample3.html', text='sample 3 repetition'),
                 Link(url='http://example.com/sample3.html', text='sample 3 repetition with fragment')
             ])