fix: add whitespace before product name (#358)

Author: yanghua

tosfs/core.py

@@ -258,7 +258,7 @@ def __init__(
             proxy_username=proxy_username,
             proxy_password=proxy_password,
             except100_continue_threshold=except100_continue_threshold,
-            user_agent_product_name="EMR",
+            user_agent_product_name=" EMR",
             user_agent_soft_name="TOSFS",
             user_agent_soft_version=Version.version,
             user_agent_customized_key_values={"revision": Version.revision},