Add lost removals .yml files

What does this MR do and why?

As a part of the removal of the removals folder, several .yml files were deleted, including breaking changes. A customer report explained the unexpected change without proper notice, which lead to the investigation of this behaviour. The breaking change was added for reference in 16.0 docs, but did not include a deprecation notice.

I was able to identify the following files were both announced for removal and removed, in the same release, so did not have deprecation notices created:

for release in "14.0" "14.1" "14.2" "14.3" "14.4" "14.5" "14.6" "14.7" "14.8" "14.9" "14.10" "15.1" "15.2" "15.3" "15.4" "15.5" "15.6" "15.7" "15.8" "15.9" "15.10" "15.11" "16.0" "16.1" "16.2"; do grep -r -l "announcement_milestone: \"$release\"" . | xargs grep "removal_milestone: \"$release\""; done
./14_9/removal_monitor_respond_integrated_error_tracking.yml:  removal_milestone: "14.9"
./15_7/15-7-remove-flowdock-integration.yml:  removal_milestone: "15.7"  # (required) The milestone when this feature is being removed.
./15_9/15-9-omniauth-authentiq.yml:  removal_milestone: "15.9"  # (required) The milestone when this feature is being removed.
./16_0/16-0-source-code-branch-push.yml:  removal_milestone: "16.0"
./16_0/16.0-eol-windows-server-2004-and-20H2.yml:  removal_milestone: "16.0"  # (required) The milestone when this feature is being removed.

All of these files have been re-created from as they were prior to deletion.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.