Merge branch '251-doc-upgrade' into 'develop'

Resolve "Move upgrade TOC under installation"

Closes #251

See merge request funkwhale/funkwhale!217

changes/changelog.d/251.doc

+Moved upgrade doc under install doc in TOC (#251)

docs/index.rst

@@ -14,11 +14,11 @@ Funkwhale is a self-hosted, modern free and open-source music server, heavily in
    users/index
    features
    installation/index
+   upgrading
    configuration
    importing-music
    federation
    api
-   upgrading
    third-party
    contributing
    changelog