build: remove unused rollup.config.js files (#28646)

Since we build and publish the individual packages
using Bazel and `build.sh` has been removed, we can
safely remove the `rollup.config.js` files which are no
longer needed because the `ng_package` bazel rule
automatically handles the rollup settings and globals.

PR Close #28646

packages/bazel/src/ng_package/BUILD.bazel

@@ -3,10 +3,7 @@ package(default_visibility = ["//visibility:public"])
 load("@build_bazel_rules_nodejs//:defs.bzl", "nodejs_binary")
 load("@build_bazel_rules_typescript//:defs.bzl", "ts_library")
 
-exports_files([
-    "rollup.config.js",
-    "ng_package.bzl",
-])
+exports_files(["ng_package.bzl"])
 
 ts_library(
     name = "lib",