Developer form footers doesn't show a shadow anymore

Description of problem:

User expects a shadow on the form footer when the add page content is longer then the viewport shows. This was shown in 4.8.

Prerequisites (if any, like setup, operators/versions):

None

Steps to Reproduce

1. Switch to developer perspective
2. Add page
3. Import from Git for example

Actual results:

No shadow at the top of the form footer when the content view is scrollable.

Expected results:

A shadow at the top of the form footer when the content view is scrollable.

Reproducibility (Always/Intermittent/Only Once):

Always

Build Details:

Happen on a cluster (4.9.0-0.nightly-2021-07-07-021823)
and local development (4.9 master, tested with 0588bc0f0b838ae448a68f35c5424f9bbfc65bc9)

Additional info:

None