docs: Fix typos in documentation: local_state.md and machine.md

[mdqst]

Description

I noticed a couple of minor typos that could cause confusion:

1. File: docs/general/local_state.md
   Original: "a contextually changes, which refers to changes made inside the current execution context."
   Fixed: Removed the unnecessary "a" to make it: "contextual changes, which refers to changes made inside the current execution context."

2. File: docs/general/machine.md
   Original: "used a volatile space to store data during execution."
   Fixed: Adjusted for grammatical correctness by changing it to: "used as volatile space to store data during execution."

Time spent on this PR: 17 mins

Pull request type

Please check the type of change your PR introduces:

• Documentation content changes

[Eikix]

Sorry for the late reply and lack of review. We've been pausing the development of kakarot for now.

I'm cognizant that you spent some time doing this PR, so thank you. I will have to close it since I am cleaning a bit the repo and preparing for archival.

Archiving the repo will solve issue of people working on stuff while we are not accepting new PRs.
Thanks for understanding