fix(playground): trim quotes from environment variables

[jtan-brex]

Description

This trims the quotes from environment variables set via substation playground to mimic the behaviour of export in bash.

Motivation and Context

Often times environment variables are copied from cloud providers eg AWS identity center. Copied token would have "" wrapped and those will be trimmed by export locally.
The os.Setenv will treat the "" as literal, this difference handling cause authentication failure.

How Has This Been Tested?

Build and tested locally.

Types of changes

• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.