patch level releases and EOL of 3.0, 3.1

[Regina Obe]

> We're still officially supporting releases as old as 3.0 (2018), and 3.6.0 was
> released before the patch-level of all branches, can we take the chance to
> EOL some branches after a last release ?
> 
> According to https://postgis.net/development/versions_eol/#end-of-life-eol
> we're supposed to maintain minor versions for 2-4 years, this would mean
> settign EOL flags to anything whose .0 was released before 2021, thus:
> 
>   - 3.0 (2019)
>   - 3.1 (2020)
> 
> So do you agree about doing the following releases ?
> 
>   - 3.0.12 (and EOL)
>   - 3.1.13 (and EOL)
>   - 3.2.9
>   - 3.3.9
>   - 3.4.5
>   - 3.5.4
> 
> After that we'd need to update
> https://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS#PostGISSup
> portMatrix
> 
> --strk;

I'm fine with EOLing 3.0, but I think we should wait till 3.7 is released before we EOL 3.1.
I just feel it's bad practice to EOL two minor versions at once.