Fixed a grammatical mistake in the docs (#1201)

docs/guides/primer/usage_pattern.md

@@ -29,7 +29,7 @@ text_list = [text1, text2, ...]
 documents = [Document(t) for t in text_list]
 ```
 
-A Document represents a lightweight container around the data source. You can now to choose to proceed with one of the 
+A Document represents a lightweight container around the data source. You can now choose to proceed with one of the 
 following steps:
 1. Feed the Document object directly into the index (see section 3).
 2. First convert the Document into Node objects (see section 2).