Upgrade to Chai 5.x (#10732)

* remove chai-string plugin

* upgrade chai and sinon-chai

* update chai imports

* migrate badge-maker tests to ESM

services/github/auth/acceptor.spec.js

@@ -114,10 +114,11 @@ describe('Github token acceptor', function () {
         const res = await got.post(`${baseUrl}/github-auth/done`, {
           body: form,
         })
-        expect(res.body).to.startWith(
-          '<p>Shields.io has received your app-specific GitHub user token.',
-        )
-
+        expect(
+          res.body.startsWith(
+            '<p>Shields.io has received your app-specific GitHub user token.',
+          ),
+        ).to.be.true
         expect(onTokenAccepted).to.have.been.calledWith(fakeAccessToken)
       })
     })