fix(core): Improve the startup error when EXECUTIONS_PROCESS is set (#8630)

Co-authored-by: Omar Ajoue <krynble@gmail.com>

packages/cli/src/config/schema.ts

@@ -234,12 +234,11 @@ export const schema = {
 	},
 
 	executions: {
-		// By default workflows get always executed in the main process.
 		// TODO: remove this and all usage of `executions.process` when we're sure that nobody has this in their config file anymore.
 		process: {
-			doc: 'Own mode has been removed and is only here for backwards compatibility of config files. N8n will use main mode for executions unless `executions.mode` is set to `queue`.',
-			format: ['main', 'own', 'IGNORED'] as const,
-			default: 'IGNORED',
+			doc: 'Deprecated key, that will be removed in the future. Please remove it from your configuration and environment variables to prevent issues in the future.',
+			format: String,
+			default: '',
 			env: 'EXECUTIONS_PROCESS',
 		},
 		mode: {