build(docs-infra): remove obsolete content from `example-config.json` files (#36015)

The `build` and `run` properties in `example-config.json` are only used
in example projects of type `systemjs`. In CLI-type projects, `build`
and `run` are ignored.

PR Close #36015

aio/content/examples/feature-modules/example-config.json

@@ -1,4 +0,0 @@
-{
-  "build": "build:cli",
-  "run": "serve:cli"
-}

aio/content/examples/lazy-loading-ngmodules/example-config.json

@@ -1,4 +0,0 @@
-{
-  "build": "build:cli",
-  "run": "serve:cli"
-}

aio/content/examples/ngmodules/example-config.json

@@ -1,4 +0,0 @@
-{
-  "build": "build:cli",
-  "run": "serve:cli"
-}

aio/content/examples/providers/example-config.json

@@ -1,4 +0,0 @@
-{
-  "build": "build:cli",
-  "run": "serve:cli"
-}