Consistent use of non-pointer fields in URL option structs

[Not-Dhananjay-Mishra]

As discuses in comment we should NOT use pointers for URL struct tags.

Example :

Currently (wrong) -

go-github/github/orgs_audit_log.go

Lines 15 to 21 in e5024aa

	type GetAuditLogOptions struct {
	Phrase *string `url:"phrase,omitempty"` // A search phrase. (Optional.)
	Include *string `url:"include,omitempty"` // Event type includes. Can be one of "web", "git", "all". Default: "web". (Optional.)
	Order *string `url:"order,omitempty"` // The order of audit log events. Can be one of "asc" or "desc". Default: "desc". (Optional.)
	ListCursorOptions
	}

---

Correct -

 type GetAuditLogOptions struct { 
 	Phrase  string `url:"phrase,omitempty"`
 	Include string `url:"include,omitempty"`
 	Order   string `url:"order,omitempty"`  
  
 	ListCursorOptions 
 }

Task :

• Update all URL option structs to remove pointer fields
• Update the structfield linter to catch this issue going forward