Missing i18n string into the single Group manage members UI

[imath]

The "All Members" default option of the dropdown filter is not translatable. The attached patch is fixing the issue.

The Group manage members UI was introduced in 5.0, I think we need to fix this in next minor release.

[imath]

In 12530:

Groups: Make the Manage Members default role option translatable

See #8188 (branch 5.0)

[imath]

In 12531:

Groups: Make the Manage Members default role option translatable

Fixes #8188 (trunk)