Redundant test cases removed as per new chunk size calculation

[Yaminim07]

What kind of change does this PR introduce?

• Redundant unit test cases removed.

What is the current behavior?

• Chunk size was static so, parts calculation was done according to the static values

What is the new behavior (if this is a feature change)?

• Chunk size is dynamic , so parts calculation will differ here.

The above change was added in this commit earlier, https://github.com/filestack/filestack-js/pull/516/files