minor #22139 [HttpFoundation][DX] MockArraySessionStorage: phpdocs update (MacDada)
minor #22139 [HttpFoundation][DX] MockArraySessionStorage: phpdocs update (MacDada)

This PR was merged into the 2.7 branch.

Discussion
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[HttpFoundation][DX] MockArraySessionStorage: phpdocs update

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Commits
-------

967f7a7add MockArraySessionStorage: updated phpdoc for $bags so that IDE autocompletion would work

symfony/http-foundation,symfony/HttpFoundation