Deprecate dummy enterprise key 2/2 (#21328)

Following [1/2](https://github.com/twentyhq/twenty/pull/20890)

Now that all usages of hasValidEnterpriseKey has been removed in prod
and deployed, we can safely remove it altogether.

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

packages/twenty-server/src/engine/core-modules/workspace/workspace.resolver.ts

@@ -309,11 +309,6 @@ export class WorkspaceResolver {
     );
   }
 
-  @ResolveField(() => Boolean)
-  hasValidEnterpriseKey(): boolean {
-    return this.enterprisePlanService.hasValidSignedEnterpriseKey();
-  }
-
   @ResolveField(() => Boolean)
   hasValidSignedEnterpriseKey(): boolean {
     return this.enterprisePlanService.hasValidSignedEnterpriseKey();