fix: use to_snowflake for remove_role

[AstreaTSS]

What type of pull request is this?

• Non-breaking code change
• Breaking code change
• Documentation change/addition
• Tests change

Description

This makes Member.remove_role use to_snowflake instead of getting the ID directly, which can result in getting a SnowflakeObject which obviously isn't ideal.

Changes

• Replace the isinstance check with a to_snowflake call in remove_role.

Checklist

• I've formatted my code with Black
• I've ensured my code works on Python 3.10.x
• I've tested my code