Auth: Make GitHub auth's allowed_organizations be case insensitive (#66879)

* Auth: Make GitHub auth's allowed_organizations be case insensitive

* Apply code suggestion to use strings.EqualFold

pkg/login/social/github_oauth.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net/http"
 	"regexp"
+	"strings"
 
 	"golang.org/x/oauth2"
 
@@ -67,7 +68,7 @@ func (s *SocialGithub) IsOrganizationMember(client *http.Client, organizationsUr
 
 	for _, allowedOrganization := range s.allowedOrganizations {
 		for _, organization := range organizations {
-			if organization == allowedOrganization {
+			if strings.EqualFold(organization, allowedOrganization) {
 				return true
 			}
 		}