Add the ability to remove tags from traces via the SDK/API

[justinwiley]

Describe the feature or potential improvement

The example evaluation pipeline calls langfuse.fetch_traces with a tag argument, to only pull traces that have been marked as needing to be evaluated.

If the script is called multiple times, it will continue to pull the same traces, because there is no way to unset or remove a tag using the api. A time window can be passed in, but this is difficult to keep syncronized, especially if there are multiple workers in the pipeline. Its possible the script could keep track of traces already seen and skip them, but again this fails for the multiple workers.

If tags could be removed from traces this would simplify the implementation of evaluation pipelines and make for a more consistent api.

Additional information

No response