Avoid double language prefix for admin page

Problem/Motivation

Under some circumstances, redirect URI becomes https://client.ddev.site/en/en/admin/config/system/google-analytics-repo... , which leads to 404 afterwards.

Steps to reproduce

Visit /admin/config/system/google-analytics-reports-api using a language that has a prefix in the URL.

Proposed resolution

Refactor \GoogleAnalyticsReportsApiFeed::currentUrl