[GNC] Selecting GnuCash version to run Flatpak wiki might need an update

[Bruce Olson]

Would someone be able to validate this before I report a bug for the wiki?

I am running Flatpak GnuCash on Debian 13.

The wiki needs to be updated here: 
https://wiki.gnucash.org/wiki/Flatpak#:~:text=To%20run%20an%20installed%20version%20other%20than%20the%20default%3A
Selecting the GnuCash version to run --> To run an installed version 
other than the default:
`flatpak run --branch <version> org.gnucash.GnuCash`
should be updated to:
`flatpak run --branch=<version> org.gnucash.GnuCash`

This is my example from installing the latest nightly build:
I followed John's example here 
https://lists.gnucash.org/pipermail/gnucash-user/2025-November/118411.html
and compared to the wiki.

The nightly build is currently my default version:
```
$ flatpak run org.gnucash.GnuCash
This is a development version. It may or may not work.
Report bugs and other problems to gnucash-devel at gnucash.org
You can also lookup and file bug reports at https://bugs.gnucash.org
To find the last stable version, please refer to https://www.gnucash.org/
$
```

This shows the installed versions:
```
$ flatpak info org.gnucash.GnuCash
error: Multiple branches available for org.gnucash.GnuCash, you must 
specify one of: 
org.gnucash.GnuCash/x86_64/stable-C5.13-112-g46fe45570f-D5.13-1-g285f67b7, 
org.gnucash.GnuCash/x86_64/stable
$
```

I get a missing argument error if I attempt run an installed version 
other than the default using the example in the wiki:
```
$ flatpak run --branch stable org.gnucash.GnuCash
error: Missing argument for --branch
$
```

I was able to successfully launch GnuCash after updating the launch command.
```
$ flatpak run --branch=stable org.gnucash.GnuCash
$
```

Thanks,

Bruce