Revert "drinking" mention on PR template

A new mention "did not drink during coding" has been recently added to QGIS PR template.

I understand that this has to be considered as a joke. Events like codesprint sometimes include good beer, and I guess this new mention was a kind of private joke with regard to a specific situation. 

Offering beer or alcoholic beverage _alongside_ tea, coffee, juices and other alcohol-free beverages is no particular problem.

Meanwhile, I really think we should avoid this kind of reference. IT in general and OpenSource in particular, especially during events, often promote a drinking culture. This is wrong on many aspects. Some cultures ( mainly non-occidental) totally reject alcohol consumption, and we should be respectful for it.

Having a mention referring to alcohol in our PR template is really contradictory to our goal of inclusion and diversity. We should stay vigilant not to propagate a drinking culture which is opposite to our core values. We want to facilitate onboarding to the project, and a PR is one of the important steps converting users to contributors. We should keep it inclusive.

.github/PULL_REQUEST_TEMPLATE.md

@@ -13,4 +13,3 @@ Include a few sentences describing the overall goals for this PR (pull request).
 - [ ] This PR passes all existing unit tests (test results will be reported by travis-ci after opening this PR)
 - [ ] New unit tests have been added for core changes
 - [ ] I have run [the `scripts/prepare-commit.sh` script](https://github.com/qgis/QGIS/blob/master/.github/CONTRIBUTING.md#contributing-to-qgis) before each commit
-- [ ] Did not drink while coding