kdump: Apply width to the modal-dialog class instead of modal in kdump dialog
kdump: Apply width to the modal-dialog class instead of modal in kdump dialog

The previous code led to the dialog being moved to the left side of the
screen.

Fixes #12771
Closes #13649
cockpituous/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,cockpit-project/cockpit,deryni/cockpit,moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,cockpituous/cockpit,mvollmer/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpituous/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,mvollmer/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,garrett/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,mvollmer/cockpit,deryni/cockpit,cockpituous/cockpit,deryni/cockpit