documentation:infrastructure: fix typos and grammar

[Quin-Darcy]

This pull request makes several corrections to the Documentation/teaching/labs/infrastructure.rst file to improve grammar and clarity. The changes focus on fixing typos, improving sentence structure, and ensuring consistency in the document.

Grammar and typo corrections:

• Fixed grammatical issues in sentences, such as adding missing commas and correcting subject-verb agreement (e.g., "each topic has a hands-on exercises" → "each topic has a hands-on exercise").
• Corrected the misspelling of "skelton" to "skeleton" in multiple instances [1] [2].

Sentence clarity improvements:

• Improved phrasing for better readability, such as changing "you can using" to "you can use" and "before start working" to "before starting working" [1] [2].
• Simplified a sentence for clarity: "you can either use ssh or update the VM image directly".