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