Remove trailing '/' from Matomo URL.

src/lib/auditors/config.ts

@@ -149,6 +149,7 @@ function auditMatomo(audit: Audit, dataUnknown: unknown,
     errors,
     remainingKeys,
     auditHttpUrl,
+    auditFunction(url => url.replace(/\/$/, "")), // Remove trailing "/".
     auditRequire,
   )