Merge pull request #4358 from matrix-org/backport-4356-to-staging

[Backport staging] Rename slowReporter to reflect that it is CommonJS

Author: dbkr

jest.config.ts

@@ -39,7 +39,7 @@ if (env["GITHUB_ACTIONS"] !== undefined) {
 
     // if we're running against the develop branch, also enable the slow test reporter
     if (env["GITHUB_REF"] == "refs/heads/develop") {
-        reporters.push("<rootDir>/spec/slowReporter.js");
+        reporters.push("<rootDir>/spec/slowReporter.cjs");
     }
     config.reporters = reporters;
 }