docs: Update grammer and semantics in file-watch.md

[eugengi]

Description

Add minor patches to correct the docs for compose watch.

I updated a sentence containing grammar errors to improve the documentation for future readers.
Given the following sentence: "Use ignore to defined additional paths to be ignored (same syntax)"
The following patches were made:

• Modify defined to define, the correct verb tense in the given context.
• Specify ignore as an option for better clarity for first-time readers.

Related issues or tickets

After an extensive search: N/A.

Reviews

The following CONTRIBUTOR guidelines were followed:

1. Include a single file change in this PR.
2. Use an editor without automatic reformatting to avoid whitespace or line-wrapping changes.
3. Verify the changes on the preview staging deploy. (Relevant Page)

• Technical review
• Editorial review
• Product review

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