Adding new to the PR template (#13579)

.github/PULL_REQUEST_TEMPLATE.md

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+:information_source:
+Bioconda has finished the [GCC7 migration](https://github.com/bioconda/bioconda-recipes/issues/13578). If you are dealing with C/C++ or Python package it can be that you need to rebuild other dependent packages. [Bioconda utils - update-pinning](https://bioconda.github.io/updating.html#updating-recipes-for-a-pinning-change) will assist you with that. If you have any questions please use [issue 13578](https://github.com/bioconda/bioconda-recipes/issues/13578).
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 * [ ] I have read the [guidelines for bioconda recipes](https://bioconda.github.io/guidelines.html).
 * [ ] This PR adds a new recipe.
 * [ ] AFAIK, this recipe **is directly relevant to the biological sciences** (otherwise, please submit to the more general purpose [conda-forge channel](https://conda-forge.org/docs/)).