Feedback: INT8 precision for lower range is incorrect

[fabiog1901]

Page: https://www.cockroachlabs.com/docs/v24.2/int.html#names-and-aliases

as per slack, the range of a INT8 should be int -(2**63) and not -(2**63) + 1.

It also helps if you add the above calculation so you know how that big number came about.

Jira issue: DOC-10918