refactor(@schematics/angular): remove unneeded extract-i18n buildTarget option for new applications

The `buildTarget` option for the `extract-18n` builder will automatically
default to use the `build` target of the containing project. This removes
the need for projects to manually configure the target. New projects will
now be generated without this option in the `angular.json` file.

(cherry picked from commit b0ec254)

Author: clydin

packages/schematics/angular/application/index.ts

@@ -273,9 +273,6 @@ function addAppToWorkspaceFile(
       },
       'extract-i18n': {
         builder: Builders.ExtractI18n,
-        options: {
-          buildTarget: `${options.name}:build`,
-        },
       },
       test: options.minimal
         ? undefined