Revert "fix: Add explicit permissions to workflow"

[alichtman]

Reverts #39.

Context: #39 (comment)

[ghost]

Reverts #39.

Context: #39 (comment)

This change is mainly about explicitly defining GITHUB_TOKEN permissions to follow least privilege. Since no permissions are set, the workflow inherits the repo default (which can be read-write for older repos), so this makes it more explicit and avoids unnecessary access.

It also resolves the 3 "Workflow does not contain permissions" code scanning alert:

• https://github.com/facebook/bunnylol.rs/security/code-scanning/1
• https://github.com/facebook/bunnylol.rs/security/code-scanning/2
• https://github.com/facebook/bunnylol.rs/security/code-scanning/3

Agree that some warnings can come from outdated actions, but this one is specifically about missing permissions rather than action versions. Let me know if you'd prefer tightening this further (example: contents: read only).