ci: update branch in mirror workflow

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

CLIENT-SPECIFICATION: v1.5

Co-authored-by: Starbeamrainbowlabs <[email protected]>
Co-authored-by: Marco Bonelli <[email protected]>

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 <[email protected]>

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

Co-authored-by: Zlatan Vasović <[email protected]>
Co-authored-by: Matthew Peveler <[email protected]>
Co-authored-by: Marco Bonelli <[email protected]>

Client spec: clarify preferred page resolution method.

clieent spec: Add messaage to page resolution section

tldr: alter to match new client spec