fix: loosen default github endpoint check

lib/datasource/github.js

@@ -14,7 +14,7 @@ async function getDependency(purl, config) {
   // istanbul ignore if
   if (
     process.env.GITHUB_ENDPOINT &&
-    process.env.GITHUB_ENDPOINT !== 'https://api.github.com/'
+    !process.env.GITHUB_ENDPOINT.startsWith('https://api.github.com')
   ) {
     logger.debug('Removing GHE token before retrieving node releases');
     endpoint = process.env.GITHUB_ENDPOINT;

lib/workers/pr/changelog/index.js

@@ -34,7 +34,7 @@ async function getChangeLogJSON(args) {
 
   if (
     process.env.GITHUB_ENDPOINT &&
-    process.env.GITHUB_ENDPOINT !== 'https://api.github.com/'
+    !process.env.GITHUB_ENDPOINT.startsWith('https://api.github.com')
   ) {
     const parsedEndpoint = url.parse(process.env.GITHUB_ENDPOINT);
     gheBaseURL = `${parsedEndpoint.protocol}//${parsedEndpoint.hostname}/`;