Remove Github OAuth2 field - scope

Remove the optional and invalid `scope` properties of "github-login" and "github-link" passport strategies.

This will result in only retrieval of the public data as required. This is the current behavior. No breaking changes.

server/passport-providers.js

@@ -144,7 +144,6 @@ export default {
     failureRedirect: failureRedirect,
     clientID: process.env.GITHUB_ID,
     clientSecret: process.env.GITHUB_SECRET,
-    scope: ['email'],
     failureFlash: true
   },
   'github-link': {
@@ -158,7 +157,6 @@ export default {
     failureRedirect: linkFailureRedirect,
     clientID: process.env.GITHUB_ID,
     clientSecret: process.env.GITHUB_SECRET,
-    scope: ['email'],
     link: true,
     failureFlash: true,
     successFlash: [ 'We\'ve updated your profile based ',