ci: Make able to run workflow in forks with uppercase in names

[MaxymVlasov]

Description of your changes

Deal with

ERROR: invalid tag "ghcr.io/MaxymVlasov/pre-commit-terraform-712:latest": repository name must be lowercase

Found during testing changes for #712 - as I need to test all workflows without disrupting main repo

[MaxymVlasov]

I don't get why it fails here.
UPD. So that's the issue - https://github.com/orgs/community/discussions/25768#discussioncomment-10671432

[yermulnik]

I don't get why it fails here. UPD. So that's the issue - github.com/orgs/community/discussions/25768#discussioncomment-10671432

I guess the linked comment is only somewhat correct.
Try and add shell: bash to run block to ensure it runs bash rather than Ubuntu's default shell which is dash I guess (and which is pretty much POSIX'ish).

Also the simpler tolowercase in Bash is ${VER,,}. JFYI.