[REM] web_editor: remove useless _shouldDelayBlur fix

The fix that introduced `this._shouldDelayBlur = true` in
`openMediaDialog` was wrong as it was fixing a symptom rather than
the source of the problem. Later fix probably fixed the source of the
problem as the problem is not reproducible at the time of this commit.
If the symptom comes back, it ought to be fixed at it's source.

closes odoo/odoo#112216

Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>