[HttpKernel] Added a missing use statement.

Broken by #8572.
merged branch jakzal/2.3-fragment-handler-fix (PR #8653)

This PR was merged into the 2.3 branch.

Discussion
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[HttpKernel] Added a missing use statement

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

Build was broken by #8572 merged into 2.3 and master.

Commits
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ccb497a [HttpKernel] Added a missing use statement.