ephy-embed-shell: Use url char pointer for g_variant_new()

Fixes GNOME/epiphany#1252
3 jobs for FixHistoryDeleteCriticals in 6 minutes and 49 seconds (queued for 1 second)
Status Job ID Name Coverage
  .Pre
passed #794018
check-code-style

00:00:51

 
  Test
passed #794019
flatpak
flatpak

00:05:58

passed #794020
flatpak
flatpak scanbuild

00:05:05