build: fix staging release checks after auto-generating `material-experimental`  package json (#24846)
build: fix staging release checks after auto-generating `material-experimental`  package json (#24846)

We recently started auto-generating the material-experimental
package.json file to avoid duplicating the MDC version/deps
across multiple places.

The staging checks assume a `package.json` file to be visible in the
source files. For our checks it is sufficient to use the handwritten
base package.json file.
angular/components,angular/components,crisbeto/material2,angular/components,crisbeto/material2,crisbeto/material2,crisbeto/material2,angular/components