ci: update branch in mirror workflow

CLIENT-SPECIFICATION: v1.5 (tldr-pages#5428)

CLIENT-SPECIFICATION: v1.5

Co-authored-by: Starbeamrainbowlabs <sbrl@starbeamrainbowlabs.com>
Co-authored-by: Marco Bonelli <marco@mebeim.net>

Client spec: require exiting with non-zero code on missing page (tldr…

…-pages#4246)

Version of the spec bumped to 1.4

Co-authored-by: Starbeamrainbowlabs <sbrl@starbeamrainbowlabs.com>

CLIENT-SPECIFICATION: clarify fallback to english (tldr-pages#4101)

Co-authored-by: Zlatan Vasović <zlatanvasovic@gmail.com>
Co-authored-by: Matthew Peveler <matt.peveler@gmail.com>
Co-authored-by: Marco Bonelli <marco@mebeim.net>

Client spec: clarify preferred page resolution method.

clieent spec: Add messaage to page resolution section

tldr: alter to match new client spec