Increase the font-size from 10 to 12 to make it ergonomic and coherent with gnome-terminal

"A clearly legible font of at least size 12 preferably in a dark color over light background should be chosen." - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9434525/

* The default font-size for gnome-terminal in Ubuntu 22.04 is 12.
* The default font-size for mate-terminal in Ubuntu MATE 22.04 is 10.

See also:
* Trisquel issue: mate-terminal: Proposed theme profile for improved ergonomics - https://gitlab.trisquel.org/trisquel/package-helpers/-/issues/95
* mate-terminal (unpackaged): [Feature request]: Increase the font-size from 10 to 12 #440 - https://github.com/mate-desktop/mate-terminal/issues/440

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: mate-terminal 1.26.0-1ubuntu2
ProcVersionSignature: Ubuntu 5.19.0-46.47~22.04.1-generic 5.19.17
Uname: Linux 5.19.0-46-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: MATE
Date: Thu Jul 20 12:54:19 2023
InstallationDate: Installed on 2023-05-20 (61 days ago)
InstallationMedia: Ubuntu-MATE 22.04.2 LTS "Jammy Jellyfish" - Release amd64 (20230223)
SourcePackage: mate-terminal
UpgradeStatus: No upgrade log present (probably fresh install)