MujocoEnv refactor remove single line function _reset_simulation()

[Kallinteris-Andreas]

Description

removes the _reset_simulation() to clean up the MujocoEnv code

Note: _reset_simulation() is not being changed in Robotics or Meta, so it should be an issue

Validation: the test/envs/mujoco is enough

Type of change

• Refactor
• Documentation only change (no code changed)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes