Remove gallery/ (#5030)

This hasn't seen wide use and has potential security issues (#5029).

Author: JelleZijlstra

CHANGES.md

@@ -68,6 +68,7 @@
 
 <!-- For example, Docker, GitHub Actions, pre-commit, editors -->
 
+- Remove unused gallery script (#5030)
 - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is
   enabled so that only version specifiers are accepted and direct references such as
   `black @ https://...` are rejected. Users should upgrade to the latest version of the