feat: run npm dedupe at end of finalizeDependencies (#902)

## PR Checklist

- [x] Addresses an existing open issue: fixes #770
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Adds with `execaCommand` since it's already being used.

Author: JoshuaKGoldberg

src/steps/finalizeDependencies.test.ts

@@ -65,6 +65,9 @@ describe("finalize", () => {
 			  [
 			    "npx all-contributors-cli generate",
 			  ],
+			  [
+			    "pnpm dedupe",
+			  ],
 			]
 		`);
 	});
@@ -83,6 +86,9 @@ describe("finalize", () => {
 			  [
 			    "npx all-contributors-cli generate",
 			  ],
+			  [
+			    "pnpm dedupe",
+			  ],
 			]
 		`);
 	});
@@ -110,6 +116,9 @@ describe("finalize", () => {
 			  [
 			    "pnpm add @types/eslint@latest @typescript-eslint/eslint-plugin@latest @typescript-eslint/parser@latest eslint@latest eslint-plugin-deprecation@latest eslint-plugin-eslint-comments@latest eslint-plugin-jsdoc@latest eslint-plugin-n@latest eslint-plugin-regexp@latest husky@latest lint-staged@latest prettier@latest prettier-plugin-curly@latest prettier-plugin-packagejson@latest tsup@latest typescript@latest -D",
 			  ],
+			  [
+			    "pnpm dedupe",
+			  ],
 			]
 		`);
 	});

src/steps/finalizeDependencies.ts

@@ -78,4 +78,6 @@ export async function finalizeDependencies(options: Options) {
 			"-D",
 		);
 	}
+
+	await execaCommand(`pnpm dedupe`);
 }