Revert "Add link to our beloved sponsor Base"

This reverts commit 827ab62.

Author: groue

README.md

@@ -15,16 +15,6 @@
     <a href="https://github.com/groue/GRDB.swift/actions/workflows/CI.yml"><img alt="CI Status" src="https://github.com/groue/GRDB.swift/actions/workflows/CI.yml/badge.svg?branch=master"></a>
 </p>
 
----
-
-<a href="https://menial.co.uk/base/"><img alt="Base: The best SQLite database editor for macOS" src="https://raw.githubusercontent.com/groue/GRDB.swift/master/Sponsors/base.png"></a>
-
-<p align="center">
-    <strong>Thank you to <a href="https://menial.co.uk/base/">Base</a> for sponsoring GRDB</strong><br />Base is a small, powerful, comfortable SQLite editor for everyone on macOS.
-</p>
-
----
-
 **Latest release**: October 2, 2025 • [version 7.8.0](https://github.com/groue/GRDB.swift/tree/v7.8.0) • [CHANGELOG](CHANGELOG.md) • [Migrating From GRDB 6 to GRDB 7](Documentation/GRDB7MigrationGuide.md)
 
 **Requirements**: iOS 13.0+ / macOS 10.15+ / tvOS 13.0+ / watchOS 7.0+ &bull; SQLite 3.20.0+ &bull; Swift 6+ / Xcode 16+