ci(docs-infra): fix `test_docs_examples_ivy` job (#30593)

Context:
As part of the `test_docs_examples_ivy` job, we run 5 concurrent builds
on each VM (each for a different example/project). Additionally, all
example projects share the same `node_modules/` (via a symlink to
`aio/tools/examples/shared/node_modules/`), so all concurrent builds
operate on the same files.

Previously, we pre-ran ngcc with `--properties module` to process the
fesm5 bundles. Since we have switched to es2015 in 661a57d9e, we now
need the esm2015 bundles. As a result, the initial ngcc run is
redundant and ngcc runs again during each build (to process the fesm2015
bundles). Since there are 5 concurrent builds, we often end up with
multiple ngcc instances processing the same package and trying to write
to the same directories at the same time, causing a
`file already exists` error

This commit fixes it by pre-processing the esm2015 bundles, so there is
no need to re-run ngcc during each concurrent build.

Fixes #30577

PR Close #30593

aio/tools/examples/example-boilerplate.js

@@ -75,9 +75,9 @@ class ExampleBoilerPlate {
     }
 
     if (ivy) {
-      // We only need the "fesm5" bundles as the CLI webpack build does not need
+      // We only need the "es2015" bundles as the CLI webpack build does not need
       // any other formats for building and serving.
-      shelljs.exec(`yarn --cwd ${SHARED_PATH} ivy-ngcc --properties module`);
+      shelljs.exec(`yarn --cwd ${SHARED_PATH} ivy-ngcc --properties es2015`);
     }
 
     exampleFolders.forEach(exampleFolder => {