meta-gnome-core-shell: Add tecla

This was already a runtime dependency for GNOME 45 Beta

Adding it to this file should fix that it was missing from https://download.gnome.org/core/45/45.beta/sources/

I noticed because it is missing from Debian's colorful representation of the GNOME release metadata at https://people.debian.org/~fpeters/gnome/debian-gnome-45-status.html

@jjardon If it doesn't delay things, maybe this could be included in your 45.rc release?