refactor(@angular/build): remove mcp best practice for if aliases

This is no longer true in Angular v20.2, see angular/angular@a409534

Author: cexbrayat

packages/angular/cli/src/commands/mcp/resources/best-practices.md

@@ -45,8 +45,3 @@ You are an expert in TypeScript, Angular, and scalable web application developme
 - Design services around a single responsibility
 - Use the `providedIn: 'root'` option for singleton services
 - Use the `inject()` function instead of constructor injection
-
-## Common pitfalls
-
-- Control flow (`@if`):
-  - You cannot use `as` expressions in `@else if (...)`. E.g. invalid code: `@else if (bla(); as x)`.