Fix broken link (#590)

Summary:
The first link at https://fasttext.cc/docs/en/pretrained-vectors.html doesn't work. This fixes it.
Pull Request resolved: https://github.com/facebookresearch/fastText/pull/590

Reviewed By: piotr-bojanowski

Differential Revision: D9489391

Pulled By: EdouardGrave

fbshipit-source-id: f1e1f0fe6a52d3d12d7a3dbf608848d68daa6c3f

docs/pretrained-vectors.md

@@ -6,7 +6,7 @@ title: Wiki word vectors
 We are publishing pre-trained word vectors for 294 languages, trained on [*Wikipedia*](https://www.wikipedia.org) using fastText.
 These vectors in dimension 300 were obtained using the skip-gram model described in [*Bojanowski et al. (2016)*](https://arxiv.org/abs/1607.04606) with default parameters.
 
-Please note that a newer version of multi-lingual word vectors are available at: [https://fasttext.cc/docs/en/crawl-vectors.html].
+Please note that a newer version of multi-lingual word vectors are available at: [Word vectors for 157 languages](https://fasttext.cc/docs/en/crawl-vectors.html).
 
 ### Models