Fix massive action modal not showing for more than 10 associated groups

[TarekRemo]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !45027
• In the Escalation tab of a group's form, the massive action modal failed to open once the group was linked to more than 10 groups.
• This was due to manageGroup() setting ontop => false on the massive action params when $nb > 10. However, Html::showMassiveActions() only creates the modal window when ontop is true (or forcecreate is set), while the "Actions" button is always rendered. As a result, for 11+ groups the button pointed to a modal object that was never created, so clicking it did nothing.
• Fix: Removed the if ($nb > 10) { $massiveactionparams['ontop'] = false; } block.

[TarekRemo]

phpstan error doesn't come from these changes. Should I fix in this PR anyway ?

[stonebuzz]

phpstan error doesn't come from these changes. Should I fix in this PR anyway ?

Yes please =)

[TarekRemo]

phpstan error doesn't come from these changes. Should I fix in this PR anyway ?

Yes please =)

Removed the entire block because it's dead code since it's fully subsumed by the one just before it.