Fix "set block timer" error after "/plot download" with legacy-webinterface setting

[Schuwi]

Overview

Fixes "a set block timer is bound to either the current plot or you [...]" message which occurs when trying to run any /plot command after downloading a plot with /plot download when web.legacy-webinterface is true in settings.yml.

Description

Add a missing call to plot.removeRunning() in Download.javas upload method. Only the code path when Settings.Web.LEGACY_WEBINTERFACE is true was missing the running task reset call.

Submitter Checklist

• [x] Make sure you are opening from a topic branch (/feature/fix/docs/ branch (right side)) and not your main branch.
• [x] Ensure that the pull request title represents the desired changelog entry.
• [ ] ~New public fields and methods are annotated with @since TODO.~
• [x] I read and followed the contribution guidelines.