Add a linode entry about a specific error to troubleshooting.md

Description

Purpose of the PR is to provide a description of how to resolve an 'unsupported stackscript' which I faced whilst trying to deploy algo onto Linode.

Motivation and Context

I have scoured the repository and internet for this issue and it seems I've spotted a unique issue. Thus, I felt it would be helpful for others if I provided a solution to this problem.

How Has This Been Tested?

N/A since it's updating troubleshooting.md. (But I would appreciate if somebody advises on how to format hyperlinks coz I don't know whether it works properly or not).

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 not work as expected) N/A since it's updating troubleshooting.md

Checklist:

[x] I have read the CONTRIBUTING document.
[] My code follows the code style of this project.
[] My change requires a change to the documentation.
[x] I have updated the documentation accordingly.
[] I have added tests to cover my changes.
[] All new and existing tests passed.

trailofbits / algo