[DX] remplace the isXmlHttpRequest method by isAjaxRequest

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #11145
| License       | MIT

Please add ``Use isAjaxRequest instead.`` in the deprecation message