fix [github] commit since tests (#6705)

Co-authored-by: repo-ranger[bot] <39074581+repo-ranger[bot]@users.noreply.github.com>

services/github/github-commits-since.tester.js

@@ -30,7 +30,7 @@ t.create('Commits since by latest release')
   })
 
 t.create('Commits since by latest release (branch)')
-  .get('/microsoft/typescript/latest/master.json')
+  .get('/microsoft/typescript/latest/main.json')
   .expectBadge({
     label: isCommitsSince,
     message: isMetric,
@@ -44,7 +44,7 @@ t.create('Commits since by latest SemVer release')
   })
 
 t.create('Commits since by latest pre-release')
-  .get('/microsoft/typescript/latest/master.json?include_prereleases')
+  .get('/microsoft/typescript/latest/main.json?include_prereleases')
   .expectBadge({
     label: isCommitsSince,
     message: isMetric,