fix: tag in pull request gh action

[dennis-ge]

Hey @bnallapeta and @MuneebAijaz, I opened #599 but the pull request workflow is failing because of a small bug:

• The Build and Push image to ghcr registry step is using ${{ env.GHCR_IMAGE_REPOSITORY }}:${{ steps.generate_tag.outputs.new_tag }} as tag.
• However, the generate_tag step is not outputting new_tag but GIT_TAG
• Probably a copy paste error because the push workflow uses the anothrNick/github-tag-action@1.61.0 github action for generate_tag, which in turn outputs new_tag. The pull request workflow instead uses some shell commands to generate the tag
• This was introduced in Update workflows to push images to ghcr #597.

Could you please have a look?

Once this is approved, I will update my other PR.

[github-actions]

@dennis-ge Yikes! You better fix it before anyone else finds out! Build has Failed!