chore: remove 'c' from knip.jsonc extension (#1247)

## PR Checklist

- [x] Addresses an existing open issue: fixes #1246
- [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

I don't know why the trailing comma is happening... but there's no need
for the file to be `.jsonc` anyway. It only used to have comments.

Author: JoshuaKGoldberg

knip.jsonc renamed to knip.json

@@ -146,9 +146,9 @@ exports[`expected file changes > cspell.json 1`] = `
  }"
 `;
 
-exports[`expected file changes > knip.jsonc 1`] = `
-"--- a/knip.jsonc
-+++ b/knip.jsonc
+exports[`expected file changes > knip.json 1`] = `
+"--- a/knip.json
++++ b/knip.json
 @@ ... @@
  {
  	"$schema": "https://unpkg.com/knip@latest/schema.json",

script/__snapshots__/migrate-test-e2e.js.snap

@@ -8,7 +8,7 @@ import packageData from "../package.json" assert { type: "json" };
 
 const filesExpectedToBeChanged = [
 	"README.md",
-	"knip.jsonc",
+	"knip.json",
 	"package.json",
 	".eslintignore",
 	".eslintrc.cjs",

script/migrate-test-e2e.js

@@ -165,7 +165,7 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "		"src/initialize/index.ts",
 			",
 			      "to": "",
@@ -174,7 +174,7 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "		"src/migrate/index.ts",
 			",
 			      "to": "",
@@ -183,15 +183,15 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "["src/index.ts!", "script/initialize*.js"]",
 			      "to": ""src/index.ts!"",
 			    },
 			  ],
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "["src/**/*.ts!", "script/**/*.js"]",
 			      "to": ""src/**/*.ts!"",
 			    },
@@ -332,7 +332,7 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "		"src/initialize/index.ts",
 			",
 			      "to": "",
@@ -341,7 +341,7 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "		"src/migrate/index.ts",
 			",
 			      "to": "",
@@ -350,15 +350,15 @@ describe("updateLocalFiles", () => {
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "["src/index.ts!", "script/initialize*.js"]",
 			      "to": ""src/index.ts!"",
 			    },
 			  ],
 			  [
 			    {
 			      "allowEmptyPaths": true,
-			      "files": "./knip.jsonc",
+			      "files": "./knip.json",
 			      "from": "["src/**/*.ts!", "script/**/*.js"]",
 			      "to": ""src/**/*.ts!"",
 			    },

src/steps/updateLocalFiles.test.ts

@@ -36,17 +36,17 @@ export async function updateLocalFiles(options: Options) {
 						"./README.md",
 					],
 					[/\n## Setup Scripts.*$/gs, "", "./.github/DEVELOPMENT.md"],
-					[`\t\t"src/initialize/index.ts",\n`, ``, "./knip.jsonc"],
-					[`\t\t"src/migrate/index.ts",\n`, ``, "./knip.jsonc"],
+					[`\t\t"src/initialize/index.ts",\n`, ``, "./knip.json"],
+					[`\t\t"src/migrate/index.ts",\n`, ``, "./knip.json"],
 					[
 						`["src/index.ts!", "script/initialize*.js"]`,
 						`"src/index.ts!"`,
-						"./knip.jsonc",
+						"./knip.json",
 					],
 					[
 						`["src/**/*.ts!", "script/**/*.js"]`,
 						`"src/**/*.ts!"`,
-						"./knip.jsonc",
+						"./knip.json",
 					],
 					// Edge case: migration scripts will rewrite README.md attribution
 					[

src/steps/updateLocalFiles.ts

@@ -111,7 +111,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 			}),
 		}),
 		...(!options.excludeLintKnip && {
-			"knip.jsonc": await formatJson({
+			"knip.json": await formatJson({
 				$schema: "https://unpkg.com/knip@latest/schema.json",
 				entry: ["src/index.ts!"],
 				ignoreExportsUsedInFile: {