Update mlagents envs (hopper, mlagents), remove *so in gitignore

[leonard-q]

:star2: Hello! Thanks for contributing JORLDY!

Checklist

Please check if you consider the following items.

• [v] My code follows the style guidelines of this project
• [v] My code follows the naming convention of documentation
• [v] I have commented my code, particularly in hard-to-understand areas
• [v] My changes generate no new warnings or errors

Types of changes

Please describe the types of changes! (ex. Bugfix, New feature, Documentation, ...) Bugfix

Test Configuration

• OS: Linux
• Python version: 3.8.8
• Additional libraries: None

Description

Please describe the details of your contribution The mlagents Linux and Server had errors because so was included in gitignore. .so is removed from gitignore. *.so files of Hopper and Pong env (Linux, Server) are restored.