Upgrade Git 2.26

Git 2.26.0 is scheduled to be released on March 22, containing particular improvements of interest:

• improved packfile reused git#7 (closed)
• partial clone performance improvements for blob size filters git#53 (closed)

The following items need to be completed:

• Update the gitlab-build-images (gitlab-build-images!283 (merged))
• Update Gitaly test pipeline (!1983 (merged))
• Update the GDK (gitlab-development-kit!1145 (merged))
• Update GitLab recipes (gitlab-recipes!91 (merged))
• Update Omnibus (omnibus-gitlab!4039 (merged))
  • Remove the packfile reuse patch in omnibus: https://gitlab.com/gitlab-org/omnibus-gitlab/-/tree/master/config/patches/git
• Update K8s charts in CNG and gitaly repos (gitlab-org/build/CNG!419 (merged))
• Have GitLab-Rails use it (gitlab!28578 (merged))