fix version defs

This brings the version strings defined through 'go build -ldflags' up to date with upstream.

The CLI version definition in the PKGBUILD has been broken for a while, but 1.16.17 introduced a new definition for the default image that broke actual 'cilium-cli install':

$ cilium-cli install
strconv.ParseUint: parsing "": invalid syntax

Reference: https://github.com/cilium/cilium-cli/issues/2795

.SRCINFO

 pkgbase = cilium-cli
 	pkgdesc = install, manage & troubleshoot Kubernetes clusters running Cilium
 	pkgver = 0.16.20
-	pkgrel = 1
+	pkgrel = 2
 	url = https://github.com/cilium/cilium-cli
 	arch = x86_64
 	license = APACHE