Remove the unnecessary scheduler.rs file

[steedmicro]

After the rewrite of the build infrastructure, the project structure has changed successfully.

But currently we are having one unnecessary code file in the project - ./native-link-scheduler/src/scheduler.rs.

It doesn't exist in the ./native-link-scheduler/src/lib.rs file and it isn't imported from other parts of the project.

That file exists in the bazel build file ./native-link-scheduler/src/BUILD.bazel and this line should be removed.

https://github.com/TraceMachina/native-link/blob/4cc53bc82286cce57854f6e7c2765f03932ac370/native-link-scheduler/BUILD.bazel#L19

It seems like this file's content is splitted into two files - action_scheduler.rs and worker_scheduler.rs.

I've double-checked other files of the project and confirmed that other files are okay and they are imported at least once inside the project.

Having a duplicate and unncessary file inside the project might add complexity to the project structure.