README.adoc: update documentation about branches and naming

The names were changed:
* v4.0 -> hbk
* v4.1 -> hbl
* v5.0 -> hbd

README.adoc

@@ -15,14 +15,14 @@ command `compile_pkgs --help` for a list of available commands, generic options,
 and their brief descriptions.
 
 Before you started you need to choose what version of Turris OS you want to
-build. There are development versions in branches named after future release.
-Those are for example `v4.0` for Turris OS 4.0.X releases or `v4.1` for Turris OS
-4.1.X releases. Then there are old releases that are tags. Those are in format of
-for example `v4.0.0` for Turris OS 4.0.0 or `v4.1.2` for Turris OS 4.1.2.
+build. There are development versions in branches named `hbk`, `hbl` and `hbd`
+(see link:WORKFLOW.adoc[workflow]). Then there are tagged final releases. Those
+are in format of for example `v4.0.0` for Turris OS 4.0.0 or `v4.1.2` for Turris
+OS 4.1.2.
 
 To get to appropriate version you have to run command like this:
-`git checkout v4.0` where in this case this takes you to development branch for
-Turris OS 4.0.X versions.
+`git checkout hbk` where in this case this takes you to development branch for
+Turris OS fixup releases.
 
 It is advised to build the latest release version as with that you are most likely
 to get to the end. To get latest version you can do: