prompt updates (#414)

<!-- This is an auto-generated comment: release notes by OSS CodeRabbit
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### Summary by CodeRabbit

**Refactor:**
- Updated the instructions in the review template for providing
replacement snippets. The new format uses `diff` instead of
`suggestion`, enhancing clarity and consistency.

> 🎉 Here's to the code that we refine, 🥂
> 
> With each pull request, it shines more divine. ✨
> 
> A tweak in the template, a small change indeed, 📝
> 
> But it guides us better, in our coding creed. 🚀
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src/prompts.ts

@@ -137,21 +137,21 @@ the system.
 Use Markdown format for review comment text and fenced code blocks for code 
 snippets. 
 
-If necessary, suggest new code snippets using the relevant language identifier in 
+If needed, suggest new code snippets using the relevant language identifier in 
 the fenced code blocks. These snippets may be added to a different file (e.g. 
 test cases), or within the same file at locations outside the provided hunks. 
 Multiple new code snippets are allowed within a single review section.
 
-If necessary, provide a replacement snippet to fix an issue by using fenced code 
-blocks using the \`diff\` format, marking additions with \`+\` and deletions
-with \`-\`. The line number range for the review section that includes the 
-replacement snippet must map exactly to the line number range that has to be 
-completely replaced within the new hunk. If less than 10 lines of the hunk have 
-to be replaced then you may alternatively use the \`suggestion\` format. You must 
-carefully include any lines of code that remain unchanged in the replacement 
-snippet to avoid issues when the replacement snippet is committed as-is. 
-Replacement snippet must be complete, correctly formatted & indented and 
-without the line number annotations. 
+If needed, provide a replacement snippet to fix an issue by using fenced code 
+blocks using the \`diff\` as the format, clearly marking the lines that need be
+added or removed with \`+\` and \`-\` respectively. The line number range for 
+the review section that includes the replacement snippet must map exactly to the 
+line number range that has to be completely replaced within the new hunk. 
+If less than 10 lines of the hunk have to be replaced then you may alternatively 
+use the \`suggestion\` format. You must carefully include any lines of code that 
+remain unchanged in the replacement snippet to avoid issues when the replacement 
+snippet is committed as-is. Replacement snippet must be complete, correctly 
+formatted & indented and without the line number annotations.
 
 If there are no issues found on a line range, you MUST respond with the 
 text \`LGTM!\` for that line range in the review section.