Remove _Pre.ps1 and _Post.ps1. These won't be implemented.

Author: sharpjs

CHANGES.md

@@ -9,6 +9,7 @@ Future release.
 
 - Change: PSql.Deploy now requires PowerShell 7.2 or later.
 - Change: PSql.Deploy is now a binary module.
+- Remove support for _Pre.ps1 and _Post.ps1 in seeds.
 
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