Remove stale "Add case" snippet

The reflection-driven implementation of Add no longer contains a huge boilerplate `switch` statement so we no longer need a snippet for the boilerplate.

.vscode/koboldsimsnippets.code-snippets

@@ -15,13 +15,4 @@
 	// 	],
 	// 	"description": "Log output to console"
 	// }
-	"KoboldMine Add case": {
-		"scope": "go",
-		"prefix": "case",
-		"body": [
-			"case ${1:field}:",
-			"\tk.${1:field} += amount",
-			"\treturn nil",
-		],
-	}
 }