Remove symlinks to assertions.js

[alxndrsn]

For easier understanding of what's going on with the assertions.js file, where it's included from, and what context it's used in.

Also these paths to not seem to be referenced from anywhere.

What has been done to verify that this works as intended?

Tests continue to pass.

Why is this the best possible solution? Were any other approaches considered?

No other options were considered.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

No change - this is test code.

Does this change require updates to the API documentation? If so, please update docs/api.yaml as part of this PR.

No.

Before submitting this PR, please make sure you have:

• run make test and confirmed all checks still pass OR confirm CircleCI build passes
• verified that any code from external sources are properly credited in comments or that everything is internally sourced