fix(api/webhook): build approval for fork-no-write

[jbrockopp]

This change resolves an issue with the new build approval feature introduced in v0.23:

https://github.com/go-vela/community/blob/main/releases/v0.23.md

The issue is builds triggered from a fork by a user with admin perms were being forced to wait for an approval.

This is unexpected behavior because the repos in question have a build approval policy of fork-no-write:

https://github.com/go-vela/types/blob/v0.23.2/constants/repo.go#L26-L28

After successfully reproducing the issue locally, I was able to determine the code causing this:

server/api/webhook/post.go

Lines 773 to 786 in 1809638

	case constants.ApproveForkNoWrite:
	// determine if build sender has write access to parent repo. If not, this call will result in an error
	_, err = scm.FromContext(c).RepoAccess(ctx, b.GetSender(), u.GetToken(), r.GetOrg(), r.GetName())
	if err != nil {
	err = gatekeepBuild(c, b, repo, u)
	if err != nil {
	util.HandleError(c, http.StatusInternalServerError, err)
	}
	return
	}
	fallthrough
	case constants.ApproveOnce:

This code is setup to check if the build sender has access to the repo:

• if they don't, then we call the function to gatekeep the build until an approval is provided
• if they do, then we fallthrough to the first-time approval policy case statement

After this change, we'll no longer fallthrough to the first-time approval policy case statement.

[codecov]

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Additional details and impacted files

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[ecrupper]

thanks!