Drop two datasets from steganography (openai#1481)

Removing two datasets:
- PiC/phrase_similarity
- vicgalle/alpaca-gpt4

Impact on Steganography:
- Only marginal change in data distribution.
- We modify the sampling counts such that we have the same total number
of samples as before.
- Did not re-run results; absolute scores should change but qualitative
interpretation of eval will not be different.

---

Piggybacking this PR to add a small fix for the OpenAIAssistantsSolver
which was causing tests to fail.

evals/registry/data/steganography/LICENSE

@@ -2,10 +2,6 @@ Abirate/english_quotes:
 License: Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/legalcode.txt
 Source: https://huggingface.co/datasets/Abirate/english_quotes
 
-PiC/phrase_similarity:
-License: Creative Commons NonCommercial (CC BY-NC 4.0) https://creativecommons.org/licenses/by-nc/4.0/legalcode
-Source: https://huggingface.co/datasets/PiC/phrase_similarity
-
 wikipedia:
 License: Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA): https://en.wikipedia.org/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_3.0_Unported_License and the GNU Free Documentation License (GFDL): https://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License
 Source: https://huggingface.co/datasets/wikipedia
@@ -25,7 +21,3 @@ Source: https://huggingface.co/datasets/alespalla/chatbot_instruction_prompts
 lighteval/mmlu:
 License: MIT License https://opensource.org/license/mit/
 Source: https://huggingface.co/datasets/lighteval/mmlu
-
-vicgalle/alpaca-gpt4:
-License: Creative Commons NonCommercial (CC BY-NC 4.0) https://creativecommons.org/licenses/by-nc/4.0/legalcode
-Source: https://huggingface.co/datasets/vicgalle/alpaca-gpt4

evals/solvers/openai_assistants_solver.py

@@ -51,11 +51,11 @@ def __init__(
  tools: list[Dict[str, Any]] = [],
  file_paths: list[str] = [],
  assistant: Optional[Assistant] = None,
- thread: Optional[Thread] = client.beta.threads.create(),
+ thread: Optional[Thread] = None,
  registry: Any = None,
  ):
  self.model = model
- self.thread = thread
+ self.thread = thread if thread else client.beta.threads.create()
  self.tools = tools
  self.all_uploaded_files = []
  if not assistant: