Bump git-sync version to v4.4.0

[ChenYi015]

Purpose of this PR

Proposed changes:

• Bump git-sync to v4.4.0 and update git-sync image
• Replace deprecated GIT_SYNC_* environment variables with the GITSYNC_* ones, including:
  • GIT_SYNC_REPO -> GITSYNC_REPO
  • GIT_SYNC_ROOT -> GITSYNC_ROOT
  • GIT_SYNC_ONE_TIME -> GITSYNC_ONETIME

Note:

• Env GIT_SYNC_DEST is kept the same as before as it was not renamed to GITSYNC_DEST in git-sync.

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

git-sync ref: https://github.com/kubernetes/git-sync/blob/69eb59185a073d4a08362d07bbe6459311027746/main.go.

[google-oss-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from chenyi015. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment