Remove env variables subprocess call

Given that the parent process includes variables like HF_TOKEN, it's safer to not pass in any env variables to the subprocess because there is always the chance that the script could get maliciously modified for instance to extract HF tokens.

**Test plan**
I tested these changes in my private space and converted a model and saw that it was correctly created

app.py

@@ -1,7 +1,9 @@
-import streamlit as st
-from huggingface_hub import HfApi
 import os
 import subprocess
+import sys
+
+from huggingface_hub import HfApi
+import streamlit as st
 
 HF_TOKEN = st.secrets.get("HF_TOKEN") or os.environ.get("HF_TOKEN")
 HF_USERNAME = (
@@ -51,7 +53,7 @@ if input_model_id:
             with st.spinner("Converting model..."):
                 output = subprocess.run(
                     [
-                        "python",
+                        sys.executable,
                         "-m",
                         "scripts.convert",
                         "--quantize",
@@ -61,6 +63,7 @@ if input_model_id:
                     cwd=TRANSFORMERS_REPOSITORY_PATH,
                     capture_output=True,
                     text=True,
+                    env={}
                 )
 
             model_folder_path = (