Fix in docs: pipe(docs) instead of pipe(texts) (#5680)

Very minor fix in docs, specifically in this part:

```
 matcher = PhraseMatcher(nlp.vocab)
>   for doc in matcher.pipe(texts, batch_size=50):
>       pass
```

`texts` suggests the input is an iterable of strings. I replaced it for `docs`.

website/docs/api/phrasematcher.md

@@ -91,7 +91,7 @@ Match a stream of documents, yielding them in turn.
 > ```python
 >   from spacy.matcher import PhraseMatcher
 >   matcher = PhraseMatcher(nlp.vocab)
->   for doc in matcher.pipe(texts, batch_size=50):
+>   for doc in matcher.pipe(docs, batch_size=50):
 >       pass
 > ```