Issue template link points to wrong address

## Which page or section is this issue related to?
### CONTRIBUTING.md
Under the "Submitting Issues" section of the Contributing guide, there is a link to an 'issue template' but the link only leads to creating a new issue with no template. Here is the sentence: "Our [issue template](https://github.com/explosion/spaCy/issues/new) helps you remember the most important details to include." It may be better to link to [this page for issues](https://github.com/explosion/spaCy/issues/new/choose) instead.

https://github.com/explosion/spaCy/blob/master/CONTRIBUTING.md#submitting-issues

Here is [the PR](https://github.com/explosion/spaCy/pull/13587) I submitted for this.