docs: fix current_release number retrieval
docs: fix current_release number retrieval

Getting the current release number by extracting the first four
characters from the string read from file VERSION is gonna bite sooner
or later. Let's get the proper major and minor fields instead,
especially because we already parsed them a few lines above.

Signed-off-by: Quentin Monnet <d6b8e48afb2534b213e391cab43016505747a234@isovalent.com>

michi-covalent/cilium,tgraf/cilium,cilium-team/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,cilium-team/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium