Add Zoho to the list of broken providers

As per the documentation https://www.zoho.com/crm/help/api/v2/#generate-access

The oauth2 implementation for Zoho is broken in other ways as well, e.g. by having scopes comma separated instead of space separated as the standard says. But won't (and shouldn't) be handled by this project as per #119.

Change-Id: I450391ac92cbb02e6ba6a21e4afcc4dd0d6849b4
GitHub-Last-Rev: ba758b0
GitHub-Pull-Request: #333
Reviewed-on: https://go-review.googlesource.com/c/142880
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

internal/token.go

@@ -133,6 +133,7 @@ var brokenAuthHeaderProviders = []string{
 	"https://whats.todaysplan.com.au/rest/oauth/access_token",
 	"https://stackoverflow.com/oauth/access_token",
 	"https://account.health.nokia.com",
+	"https://accounts.zoho.com",
 }
 
 // brokenAuthHeaderDomains lists broken providers that issue dynamic endpoints.