Suggestion: Add upgrade in-place instructions for code repository installations performing minor upgrades

**Documentation version**

2.7, 2.8

**Relevant documentation pages**

* https://www.accesstomemory.org/docs/latest/admin-manual/installation/upgrading/

**Description**

A suggestion from the User Forum, 2023-06-02: https://groups.google.com/g/ica-atom-users/c/f5_Qw_Mhfuk/m/U1AIyIEHAwAJ

We offer 2 methods of installing in our primary documentation:

* [Option 1](https://www.accesstomemory.org/docs/latest/admin-manual/installation/ubuntu/#option-1-download-the-tarball) is to install from the downloadable tarball
* [Option 2](https://www.accesstomemory.org/docs/latest/admin-manual/installation/ubuntu/#option-2-check-out-the-code-from-our-git-repository) is to install from the GitHub code repository

Because Artefactual has consistently avoided including database schema migrations in point releases, it is generally possible to upgrade in place when Option 2 is followed. However, this is not well documented or clear to end-users with varying degrees of experience with software maintenance and git, and there are numerous examples in the forum (including in the link above) of users seeking guidance on how to perform minor upgrades in place and avoid needing to do an entire install for some generally minor fixes.

**Recommended fix**

As is correctly noted in the forum post, since we support Option 2 as an installation method, we should consider including a brief section in the Upgrade page about how to upgrade in place for those who followed the code repository installation method originally.

Start with the documented upgrading page and the Ubuntu installation page's Option 2, then review the linked User Forum discussion for the missing guidance. Document the in-place minor-upgrade process for installations made from the Git repository, with enough context for users of varying Git and maintenance experience to follow it.

Written by the indexing model from the issue text.