CONTRIBUTING: Remove now-unneeded mass ping section

This is not a problem anymore with the parent commit

CONTRIBUTING.md

@@ -193,19 +193,12 @@ The last checkbox is about whether it fits the guidelines in this `CONTRIBUTING.
 [rebase]: #rebasing-between-branches-ie-from-master-to-staging
 
 From time to time, changes between branches must be rebased, for example, if the
-number of new rebuilds they would cause is too large for the target branch. When
-rebasing, care must be taken to include only the intended changes, otherwise
-many CODEOWNERS will be inadvertently requested for review. To achieve this,
-rebasing should not be performed directly on the target branch, but on the merge
-base between the current and target branch. As an additional precautionary measure,
-you should temporarily mark the PR as draft for the duration of the operation.
-This reduces the probability of mass-pinging people. (OfBorg might still
-request a couple of persons for reviews though.)
+number of new rebuilds they would cause is too large for the target branch.
 
 In the following example, we assume that the current branch, called `feature`,
 is based on `master`, and we rebase it onto the merge base between
-`master` and `staging` so that the PR can eventually be retargeted to
-`staging` without causing a mess. The example uses `upstream` as the remote for `NixOS/nixpkgs.git`
+`master` and `staging` so that the PR can be retargeted to
+`staging`. The example uses `upstream` as the remote for `NixOS/nixpkgs.git`
 while `origin` is the remote you are pushing to.
 
 
@@ -234,36 +227,6 @@ git status
 git push origin feature --force-with-lease
 ```
 
-#### Something went wrong and a lot of people were pinged
-
-It happens. Remember to be kind, especially to new contributors.
-There is no way back, so the pull request should be closed and locked
-(if possible). The changes should be re-submitted in a new PR, in which the people
-originally involved in the conversation need to manually be pinged again.
-No further discussion should happen on the original PR, as a lot of people
-are now subscribed to it.
-
-The following message (or a version thereof) might be left when closing to
-describe the situation, since closing and locking without any explanation
-is kind of rude:
-
-```markdown
-It looks like you accidentally mass-pinged a bunch of people, which are now subscribed
-and getting notifications for everything in this pull request. Unfortunately, they
-cannot be automatically unsubscribed from the issue (removing review request does not
-unsubscribe), therefore development cannot continue in this pull request anymore.
-
-Please open a new pull request with your changes, link back to this one and ping the
-people actually involved in here over there.
-
-In order to avoid this in the future, there are instructions for how to properly
-rebase between branches in our [contribution guidelines](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#rebasing-between-branches-ie-from-master-to-staging).
-Setting your pull request to draft prior to rebasing is strongly recommended.
-In draft status, you can preview the list of people that are about to be requested
-for review, which allows you to sidestep this issue.
-This is not a bulletproof method though, as OfBorg still does review requests even on draft PRs.
-```
-
 ## How to backport pull requests
 [pr-backport]: #how-to-backport-pull-requests