feat(compiler): set enableLegacyTemplate to false by default (#18756)

BREAKING CHANGE: the compiler option `enableLegacyTemplate` is now disabled by default as the `<template>` element has been deprecated since v4. Use `<ng-template>` instead. The option `enableLegacyTemplate` and the `<template>` element will both be removed in Angular v6.
PR Close #18756

packages/compiler-cli/src/codegen.ts

@@ -101,7 +101,7 @@ export class CodeGenerator {
       translations: transContent,
       i18nFormat: cliOptions.i18nFormat || undefined,
       locale: cliOptions.locale || undefined, missingTranslation,
-      enableLegacyTemplate: options.enableLegacyTemplate !== false,
+      enableLegacyTemplate: options.enableLegacyTemplate === true,
       enableSummariesForJit: options.enableSummariesForJit !== false,
       preserveWhitespaces: options.preserveWhitespaces,
     });